tests: remove legacy Topo class (fixes many pylint errors)

Signed-off-by: Christian Hopps <chopps@labn.net>

174 files changed, 2503 insertions, 4356 deletions

diff --git a/tests/topotests/all_protocol_startup/test_all_protocol_startup.py b/tests/topotests/all_protocol_startup/test_all_protocol_startup.py
index 41597c449..52526e0c7 100644
--- a/tests/topotests/all_protocol_startup/test_all_protocol_startup.py
+++ b/tests/topotests/all_protocol_startup/test_all_protocol_startup.py
@@ -34,8 +34,6 @@ import pytest
 import glob
 from time import sleep
 
-from lib.micronet_compat import Mininet, Topo
-
 from functools import partial
 
 pytestmark = [
@@ -50,6 +48,7 @@ pytestmark = [
 
 sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 from lib import topotest
+from lib.topogen import Topogen, get_topogen
 
 fatal_error = ""
 
@@ -61,24 +60,10 @@ fatal_error = ""
 #####################################################
 
 
-class NetworkTopo(Topo):
-    "All Protocol Startup Test"
-
-    def build(self, **_opts):
-
-        # Setup Routers
-        router = {}
-        #
-        # Setup Main Router
-        router[1] = topotest.addRouter(self, "r1")
-        #
-
-        # Setup Switches
-        switch = {}
-        #
-        for i in range(0, 10):
-            switch[i] = self.addSwitch("sw%s" % i)
-            self.addLink(switch[i], router[1], intfName2="r1-eth%s" % i)
+def build_topo(tgen):
+    router = tgen.add_router("r1")
+    for i in range(0, 10):
+        tgen.add_switch("sw%d" % i).add_link(router)
 
 
 #####################################################
@@ -89,21 +74,16 @@ class NetworkTopo(Topo):
 
 
 def setup_module(module):
-    global topo, net
     global fatal_error
 
     print("\n\n** %s: Setup Topology" % module.__name__)
     print("******************************************\n")
 
-    print("Cleanup old Mininet runs")
-    os.system("sudo mn -c > /dev/null 2>&1")
-    os.system("sudo rm /tmp/r* > /dev/null 2>&1")
-
     thisDir = os.path.dirname(os.path.realpath(__file__))
-    topo = NetworkTopo()
+    tgen = Topogen(build_topo, module.__name__)
+    tgen.start_topology()
 
-    net = Mininet(controller=None, topo=topo)
-    net.start()
+    net = tgen.net
 
     if net["r1"].get_routertype() != "frr":
         fatal_error = "Test is only implemented for FRR"
@@ -133,25 +113,22 @@ def setup_module(module):
         net["r%s" % i].loadConf("nhrpd", "%s/r%s/nhrpd.conf" % (thisDir, i))
         net["r%s" % i].loadConf("babeld", "%s/r%s/babeld.conf" % (thisDir, i))
         net["r%s" % i].loadConf("pbrd", "%s/r%s/pbrd.conf" % (thisDir, i))
-        net["r%s" % i].startRouter()
+        tgen.gears["r%s" % i].start()
 
     # For debugging after starting FRR daemons, uncomment the next line
     # CLI(net)
 
 
 def teardown_module(module):
-    global net
-
     print("\n\n** %s: Shutdown Topology" % module.__name__)
     print("******************************************\n")
-
-    # End - Shutdown network
-    net.stop()
+    tgen = get_topogen()
+    tgen.stop_topology()
 
 
 def test_router_running():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -172,7 +149,7 @@ def test_router_running():
 
 def test_error_messages_vtysh():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -228,7 +205,7 @@ def test_error_messages_vtysh():
 
 def test_error_messages_daemons():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -319,7 +296,7 @@ def test_error_messages_daemons():
 
 def test_converge_protocols():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -408,6 +385,7 @@ def test_converge_protocols():
 
 
 def route_get_nhg_id(route_str):
+    net = get_topogen().net
     output = net["r1"].cmd('vtysh -c "show ip route %s nexthop-group"' % route_str)
     match = re.search(r"Nexthop Group ID: (\d+)", output)
     assert match is not None, (
@@ -419,6 +397,7 @@ def route_get_nhg_id(route_str):
 
 
 def verify_nexthop_group(nhg_id, recursive=False, ecmp=0):
+    net = get_topogen().net
     # Verify NHG is valid/installed
     output = net["r1"].cmd('vtysh -c "show nexthop-group rib %d"' % nhg_id)
 
@@ -457,7 +436,7 @@ def verify_route_nexthop_group(route_str, recursive=False, ecmp=0):
 
 def test_nexthop_groups():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -606,7 +585,7 @@ def test_nexthop_groups():
 
 def test_rip_status():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -666,7 +645,7 @@ def test_rip_status():
 
 def test_ripng_status():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -733,7 +712,7 @@ def test_ripng_status():
 
 def test_ospfv2_interfaces():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -818,7 +797,7 @@ def test_ospfv2_interfaces():
 
 def test_isis_interfaces():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -884,7 +863,7 @@ def test_isis_interfaces():
 
 def test_bgp_summary():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -1045,7 +1024,7 @@ def test_bgp_summary():
 
 def test_bgp_ipv6_summary():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -1140,6 +1119,7 @@ def test_bgp_ipv6_summary():
 
 
 def test_nht():
+    net = get_topogen().net
     print("\n\n**** Test that nexthop tracking is at least nominally working ****\n")
 
     thisDir = os.path.dirname(os.path.realpath(__file__))
@@ -1188,7 +1168,7 @@ def test_nht():
 
 def test_bgp_ipv4():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -1258,7 +1238,7 @@ def test_bgp_ipv4():
 
 def test_bgp_ipv6():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -1327,7 +1307,7 @@ def test_bgp_ipv6():
 
 def test_route_map():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     if fatal_error != "":
         pytest.skip(fatal_error)
@@ -1370,7 +1350,7 @@ def test_route_map():
 
 def test_nexthop_groups_with_route_maps():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -1467,7 +1447,7 @@ def test_nexthop_groups_with_route_maps():
 
 def test_nexthop_group_replace():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -1500,7 +1480,7 @@ def test_nexthop_group_replace():
 
 def test_mpls_interfaces():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -1569,7 +1549,7 @@ def test_mpls_interfaces():
 
 def test_shutdown_check_stderr():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -1632,7 +1612,7 @@ def test_shutdown_check_stderr():
 
 def test_shutdown_check_memleak():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
diff --git a/tests/topotests/bfd_topo2/test_bfd_topo2.py b/tests/topotests/bfd_topo2/test_bfd_topo2.py
index 00431ea1f..57ce0cdf0 100644
--- a/tests/topotests/bfd_topo2/test_bfd_topo2.py
+++ b/tests/topotests/bfd_topo2/test_bfd_topo2.py
@@ -46,28 +46,6 @@ from lib.topolog import logger
 pytestmark = [pytest.mark.bfdd, pytest.mark.bgpd, pytest.mark.ospfd]
 
 
-def build(self, *_args, **_opts):
-    "Build function"
-    tgen = get_topogen(self)
-
-    # Create 4 routers.
-    for routern in range(1, 5):
-        tgen.add_router("r{}".format(routern))
-
-    switch = tgen.add_switch("s1")
-    switch.add_link(tgen.gears["r1"])
-    switch.add_link(tgen.gears["r2"])
-
-    switch = tgen.add_switch("s2")
-    switch.add_link(tgen.gears["r2"])
-    switch.add_link(tgen.gears["r3"])
-
-    switch = tgen.add_switch("s3")
-    switch.add_link(tgen.gears["r2"])
-    switch.add_link(tgen.gears["r4"])
-
-
-
 def setup_module(mod):
     "Sets up the pytest environment"
     topodef = {
@@ -76,7 +54,6 @@ def setup_module(mod):
         "s3": ("r2", "r4"),
     }
     tgen = Topogen(topodef, mod.__name__)
-    # tgen = Topogen(build, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bfd_vrf_topo1/test_bfd_vrf_topo1.py b/tests/topotests/bfd_vrf_topo1/test_bfd_vrf_topo1.py
index 125cc183c..06b20c443 100644
--- a/tests/topotests/bfd_vrf_topo1/test_bfd_vrf_topo1.py
+++ b/tests/topotests/bfd_vrf_topo1/test_bfd_vrf_topo1.py
@@ -49,33 +49,27 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bfdd, pytest.mark.bgpd]
 
 
-class BFDTopo(Topo):
-    "Test topology builder"
+def build_topo(tgen):
+    # Create 4 routers
+    for routern in range(1, 5):
+        tgen.add_router("r{}".format(routern))
 
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
-        # Create 4 routers
-        for routern in range(1, 5):
-            tgen.add_router("r{}".format(routern))
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
 
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
-
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
-
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r4"])
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r4"])
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(BFDTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_aggregate_address_origin/test_bgp_aggregate-address_origin.py b/tests/topotests/bgp_aggregate_address_origin/test_bgp_aggregate-address_origin.py
index 4fa6828ef..517154987 100644
--- a/tests/topotests/bgp_aggregate_address_origin/test_bgp_aggregate-address_origin.py
+++ b/tests/topotests/bgp_aggregate_address_origin/test_bgp_aggregate-address_origin.py
@@ -50,20 +50,17 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    for routern in range(1, 3):
+        tgen.add_router("r{}".format(routern))
 
-        for routern in range(1, 3):
-            tgen.add_router("r{}".format(routern))
-
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_aggregate_address_route_map/test_bgp_aggregate-address_route-map.py b/tests/topotests/bgp_aggregate_address_route_map/test_bgp_aggregate-address_route-map.py
index f4b988954..74c9e83ce 100644
--- a/tests/topotests/bgp_aggregate_address_route_map/test_bgp_aggregate-address_route-map.py
+++ b/tests/topotests/bgp_aggregate_address_route_map/test_bgp_aggregate-address_route-map.py
@@ -53,20 +53,17 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    for routern in range(1, 3):
+        tgen.add_router("r{}".format(routern))
 
-        for routern in range(1, 3):
-            tgen.add_router("r{}".format(routern))
-
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_aggregate_address_topo1/test_bgp_aggregate_address_topo1.py b/tests/topotests/bgp_aggregate_address_topo1/test_bgp_aggregate_address_topo1.py
index 6566a860b..4e82a61e1 100644
--- a/tests/topotests/bgp_aggregate_address_topo1/test_bgp_aggregate_address_topo1.py
+++ b/tests/topotests/bgp_aggregate_address_topo1/test_bgp_aggregate_address_topo1.py
@@ -45,27 +45,25 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class BgpAggregateAddressTopo1(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
-
-        r1 = tgen.add_router("r1")
-        r2 = tgen.add_router("r2")
-        peer1 = tgen.add_exabgp_peer(
-            "peer1", ip="10.0.0.2", defaultRoute="via 10.0.0.1"
-        )
 
-        switch = tgen.add_switch("s1")
-        switch.add_link(r1)
-        switch.add_link(peer1)
+def build_topo(tgen):
+    r1 = tgen.add_router("r1")
+    r2 = tgen.add_router("r2")
+    peer1 = tgen.add_exabgp_peer(
+        "peer1", ip="10.0.0.2", defaultRoute="via 10.0.0.1"
+    )
+
+    switch = tgen.add_switch("s1")
+    switch.add_link(r1)
+    switch.add_link(peer1)
 
-        switch = tgen.add_switch("s2")
-        switch.add_link(r1)
-        switch.add_link(r2)
+    switch = tgen.add_switch("s2")
+    switch.add_link(r1)
+    switch.add_link(r2)
 
 
 def setup_module(mod):
-    tgen = Topogen(BgpAggregateAddressTopo1, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router = tgen.gears["r1"]
diff --git a/tests/topotests/bgp_aggregator_zero/test_bgp_aggregator_zero.py b/tests/topotests/bgp_aggregator_zero/test_bgp_aggregator_zero.py
index 99c31a355..76eafbce4 100644
--- a/tests/topotests/bgp_aggregator_zero/test_bgp_aggregator_zero.py
+++ b/tests/topotests/bgp_aggregator_zero/test_bgp_aggregator_zero.py
@@ -43,22 +43,19 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class BgpAggregatorAsnZero(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
-
-        r1 = tgen.add_router("r1")
-        peer1 = tgen.add_exabgp_peer(
-            "peer1", ip="10.0.0.2", defaultRoute="via 10.0.0.1"
-        )
+def build_topo(tgen):
+    r1 = tgen.add_router("r1")
+    peer1 = tgen.add_exabgp_peer(
+        "peer1", ip="10.0.0.2", defaultRoute="via 10.0.0.1"
+    )
 
-        switch = tgen.add_switch("s1")
-        switch.add_link(r1)
-        switch.add_link(peer1)
+    switch = tgen.add_switch("s1")
+    switch.add_link(r1)
+    switch.add_link(peer1)
 
 
 def setup_module(mod):
-    tgen = Topogen(BgpAggregatorAsnZero, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router = tgen.gears["r1"]
diff --git a/tests/topotests/bgp_as_allow_in/test_bgp_as_allow_in.py b/tests/topotests/bgp_as_allow_in/test_bgp_as_allow_in.py
index 4c0142fd0..5613b75d7 100644
--- a/tests/topotests/bgp_as_allow_in/test_bgp_as_allow_in.py
+++ b/tests/topotests/bgp_as_allow_in/test_bgp_as_allow_in.py
@@ -94,19 +94,11 @@ NETWORK = {"ipv4": "2.2.2.2/32", "ipv6": "22:22::2/128"}
 NEXT_HOP_IP = {"ipv4": "Null0", "ipv6": "Null0"}
 
 
-class BGPALLOWASIN(Topo):
-    """
-    Test BGPALLOWASIN - topology 1
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function"""
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    """Build function"""
 
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
+    # Building topology from json file
+    build_topo_from_json(tgen, topo)
 
 
 def setup_module(mod):
@@ -128,7 +120,7 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(BGPALLOWASIN, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/bgp_as_wide_bgp_identifier/test_bgp_as_wide_bgp_identifier.py b/tests/topotests/bgp_as_wide_bgp_identifier/test_bgp_as_wide_bgp_identifier.py
index 046f3f80a..2f7a9cc58 100644
--- a/tests/topotests/bgp_as_wide_bgp_identifier/test_bgp_as_wide_bgp_identifier.py
+++ b/tests/topotests/bgp_as_wide_bgp_identifier/test_bgp_as_wide_bgp_identifier.py
@@ -48,21 +48,18 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    for routern in range(1, 4):
+        tgen.add_router("r{}".format(routern))
 
-        for routern in range(1, 4):
-            tgen.add_router("r{}".format(routern))
-
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_aspath_zero/test_bgp_aspath_zero.py b/tests/topotests/bgp_aspath_zero/test_bgp_aspath_zero.py
index 3c264a7da..875ff38d8 100644
--- a/tests/topotests/bgp_aspath_zero/test_bgp_aspath_zero.py
+++ b/tests/topotests/bgp_aspath_zero/test_bgp_aspath_zero.py
@@ -43,22 +43,19 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class BgpAggregatorAsnZero(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    r1 = tgen.add_router("r1")
+    peer1 = tgen.add_exabgp_peer(
+        "peer1", ip="10.0.0.2", defaultRoute="via 10.0.0.1"
+    )
 
-        r1 = tgen.add_router("r1")
-        peer1 = tgen.add_exabgp_peer(
-            "peer1", ip="10.0.0.2", defaultRoute="via 10.0.0.1"
-        )
-
-        switch = tgen.add_switch("s1")
-        switch.add_link(r1)
-        switch.add_link(peer1)
+    switch = tgen.add_switch("s1")
+    switch.add_link(r1)
+    switch.add_link(peer1)
 
 
 def setup_module(mod):
-    tgen = Topogen(BgpAggregatorAsnZero, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router = tgen.gears["r1"]
diff --git a/tests/topotests/bgp_auth/test_bgp_auth.py b/tests/topotests/bgp_auth/test_bgp_auth.py
index b13f3d6e2..48ba0cca5 100644
--- a/tests/topotests/bgp_auth/test_bgp_auth.py
+++ b/tests/topotests/bgp_auth/test_bgp_auth.py
@@ -74,76 +74,64 @@ pytestmark = [pytest.mark.bgpd, pytest.mark.ospfd]
 
 class InvalidCLIError(Exception):
     """Raise when the CLI command is wrong"""
-
     pass
 
-
-class TemplateTopo(Topo):
-    "Test topology builder"
-
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
-
-        # This function only purpose is to define allocation and relationship
-        # between routers, switches and hosts.
-        #
-        #
-        # Create routers
-        tgen.add_router("R1")
-        tgen.add_router("R2")
-        tgen.add_router("R3")
-
-        # R1-R2 1
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["R1"])
-        switch.add_link(tgen.gears["R2"])
-
-        # R1-R3 1
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["R1"])
-        switch.add_link(tgen.gears["R3"])
-
-        # R2-R3 1
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["R2"])
-        switch.add_link(tgen.gears["R3"])
-
-        # R1-R2 2
-        switch = tgen.add_switch("s4")
-        switch.add_link(tgen.gears["R1"])
-        switch.add_link(tgen.gears["R2"])
-
-        # R1-R3 2
-        switch = tgen.add_switch("s5")
-        switch.add_link(tgen.gears["R1"])
-        switch.add_link(tgen.gears["R3"])
-
-        # R2-R3 2
-        switch = tgen.add_switch("s6")
-        switch.add_link(tgen.gears["R2"])
-        switch.add_link(tgen.gears["R3"])
-
-        # R1-R2 3
-        switch = tgen.add_switch("s7")
-        switch.add_link(tgen.gears["R1"])
-        switch.add_link(tgen.gears["R2"])
-
-        # R1-R3 2
-        switch = tgen.add_switch("s8")
-        switch.add_link(tgen.gears["R1"])
-        switch.add_link(tgen.gears["R3"])
-
-        # R2-R3 2
-        switch = tgen.add_switch("s9")
-        switch.add_link(tgen.gears["R2"])
-        switch.add_link(tgen.gears["R3"])
+def build_topo(tgen):
+    # Create routers
+    tgen.add_router("R1")
+    tgen.add_router("R2")
+    tgen.add_router("R3")
+
+    # R1-R2 1
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["R1"])
+    switch.add_link(tgen.gears["R2"])
+
+    # R1-R3 1
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["R1"])
+    switch.add_link(tgen.gears["R3"])
+
+    # R2-R3 1
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["R2"])
+    switch.add_link(tgen.gears["R3"])
+
+    # R1-R2 2
+    switch = tgen.add_switch("s4")
+    switch.add_link(tgen.gears["R1"])
+    switch.add_link(tgen.gears["R2"])
+
+    # R1-R3 2
+    switch = tgen.add_switch("s5")
+    switch.add_link(tgen.gears["R1"])
+    switch.add_link(tgen.gears["R3"])
+
+    # R2-R3 2
+    switch = tgen.add_switch("s6")
+    switch.add_link(tgen.gears["R2"])
+    switch.add_link(tgen.gears["R3"])
+
+    # R1-R2 3
+    switch = tgen.add_switch("s7")
+    switch.add_link(tgen.gears["R1"])
+    switch.add_link(tgen.gears["R2"])
+
+    # R1-R3 2
+    switch = tgen.add_switch("s8")
+    switch.add_link(tgen.gears["R1"])
+    switch.add_link(tgen.gears["R3"])
+
+    # R2-R3 2
+    switch = tgen.add_switch("s9")
+    switch.add_link(tgen.gears["R2"])
+    switch.add_link(tgen.gears["R3"])
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     # ... and here it calls Mininet initialization functions.
     tgen.start_topology()
 
diff --git a/tests/topotests/bgp_basic_functionality_topo1/test_bgp_basic_functionality.py b/tests/topotests/bgp_basic_functionality_topo1/test_bgp_basic_functionality.py
index b9ad57f8b..ee241b653 100644
--- a/tests/topotests/bgp_basic_functionality_topo1/test_bgp_basic_functionality.py
+++ b/tests/topotests/bgp_basic_functionality_topo1/test_bgp_basic_functionality.py
@@ -79,13 +79,6 @@ from lib.topolog import logger
 pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
 
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/bgp_basic_functionality.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 
 # Global Variable
 KEEPALIVETIMER = 2
@@ -104,21 +97,6 @@ NETWORK = {
 }
 
 
-class CreateTopo(Topo):
-    """
-    Test BasicTopo - topology 1
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function"""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
@@ -138,7 +116,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/bgp_basic_functionality.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/bgp_blackhole_community/test_bgp_blackhole_community.py b/tests/topotests/bgp_blackhole_community/test_bgp_blackhole_community.py
index 7e78722da..aaa65004f 100644
--- a/tests/topotests/bgp_blackhole_community/test_bgp_blackhole_community.py
+++ b/tests/topotests/bgp_blackhole_community/test_bgp_blackhole_community.py
@@ -43,28 +43,25 @@ from lib.common_config import step
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    for routern in range(1, 5):
+        tgen.add_router("r{}".format(routern))
 
-        for routern in range(1, 5):
-            tgen.add_router("r{}".format(routern))
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
 
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
-
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r4"])
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r4"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_comm_list_delete/test_bgp_comm-list_delete.py b/tests/topotests/bgp_comm_list_delete/test_bgp_comm-list_delete.py
index 2c1546a3b..252475616 100644
--- a/tests/topotests/bgp_comm_list_delete/test_bgp_comm-list_delete.py
+++ b/tests/topotests/bgp_comm_list_delete/test_bgp_comm-list_delete.py
@@ -48,20 +48,17 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    for routern in range(1, 3):
+        tgen.add_router("r{}".format(routern))
 
-        for routern in range(1, 3):
-            tgen.add_router("r{}".format(routern))
-
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_communities_topo1/test_bgp_communities.py b/tests/topotests/bgp_communities_topo1/test_bgp_communities.py
index df579bc01..be0d87d22 100644
--- a/tests/topotests/bgp_communities_topo1/test_bgp_communities.py
+++ b/tests/topotests/bgp_communities_topo1/test_bgp_communities.py
@@ -69,14 +69,6 @@ from copy import deepcopy
 pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
 
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/bgp_communities.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
-
 # Global variables
 BGP_CONVERGENCE = False
 ADDR_TYPES = check_address_types()
@@ -84,21 +76,6 @@ NETWORK = {"ipv4": "2.2.2.2/32", "ipv6": "22:22::2/128"}
 NEXT_HOP_IP = {}
 
 
-class BGPCOMMUNITIES(Topo):
-    """
-    Test BGPCOMMUNITIES - topology 1
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function"""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
@@ -118,7 +95,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(BGPCOMMUNITIES, mod.__name__)
+    json_file = "{}/bgp_communities.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/bgp_communities_topo1/test_bgp_communities_topo2.py b/tests/topotests/bgp_communities_topo1/test_bgp_communities_topo2.py
index d18e65bd6..80bcae631 100644
--- a/tests/topotests/bgp_communities_topo1/test_bgp_communities_topo2.py
+++ b/tests/topotests/bgp_communities_topo1/test_bgp_communities_topo2.py
@@ -73,14 +73,6 @@ from copy import deepcopy
 pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
 
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/bgp_communities_topo2.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
-
 # Global variables
 BGP_CONVERGENCE = False
 ADDR_TYPES = check_address_types()
@@ -90,21 +82,6 @@ NETWORK = {
 }
 
 
-class BGPCOMMUNITIES(Topo):
-    """
-    Test BGPCOMMUNITIES - topology 1
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function"""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
@@ -124,7 +101,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(BGPCOMMUNITIES, mod.__name__)
+    json_file = "{}/bgp_communities_topo2.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/bgp_community_alias/test_bgp-community-alias.py b/tests/topotests/bgp_community_alias/test_bgp-community-alias.py
index 2ef30249e..cc8166029 100644
--- a/tests/topotests/bgp_community_alias/test_bgp-community-alias.py
+++ b/tests/topotests/bgp_community_alias/test_bgp-community-alias.py
@@ -43,20 +43,18 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
 
-        for routern in range(1, 3):
-            tgen.add_router("r{}".format(routern))
+def build_topo(tgen):
+    for routern in range(1, 3):
+        tgen.add_router("r{}".format(routern))
 
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_community_change_update/test_bgp_community_change_update.py b/tests/topotests/bgp_community_change_update/test_bgp_community_change_update.py
index eee9294df..472a0b955 100644
--- a/tests/topotests/bgp_community_change_update/test_bgp_community_change_update.py
+++ b/tests/topotests/bgp_community_change_update/test_bgp_community_change_update.py
@@ -62,55 +62,52 @@ from time import sleep
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
-
-        tgen.add_router("z1")
-        tgen.add_router("y1")
-        tgen.add_router("y2")
-        tgen.add_router("y3")
-        tgen.add_router("x1")
-        tgen.add_router("c1")
-
-        # 10.0.1.0/30
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["c1"])
-        switch.add_link(tgen.gears["x1"])
-
-        # 10.0.2.0/30
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["x1"])
-        switch.add_link(tgen.gears["y1"])
-
-        # 10.0.3.0/30
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["y1"])
-        switch.add_link(tgen.gears["y2"])
-
-        # 10.0.4.0/30
-        switch = tgen.add_switch("s4")
-        switch.add_link(tgen.gears["y1"])
-        switch.add_link(tgen.gears["y3"])
-
-        # 10.0.5.0/30
-        switch = tgen.add_switch("s5")
-        switch.add_link(tgen.gears["y2"])
-        switch.add_link(tgen.gears["y3"])
-
-        # 10.0.6.0/30
-        switch = tgen.add_switch("s6")
-        switch.add_link(tgen.gears["y2"])
-        switch.add_link(tgen.gears["z1"])
-
-        # 10.0.7.0/30
-        switch = tgen.add_switch("s7")
-        switch.add_link(tgen.gears["y3"])
-        switch.add_link(tgen.gears["z1"])
+def build_topo(tgen):
+    tgen.add_router("z1")
+    tgen.add_router("y1")
+    tgen.add_router("y2")
+    tgen.add_router("y3")
+    tgen.add_router("x1")
+    tgen.add_router("c1")
+
+    # 10.0.1.0/30
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["c1"])
+    switch.add_link(tgen.gears["x1"])
+
+    # 10.0.2.0/30
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["x1"])
+    switch.add_link(tgen.gears["y1"])
+
+    # 10.0.3.0/30
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["y1"])
+    switch.add_link(tgen.gears["y2"])
+
+    # 10.0.4.0/30
+    switch = tgen.add_switch("s4")
+    switch.add_link(tgen.gears["y1"])
+    switch.add_link(tgen.gears["y3"])
+
+    # 10.0.5.0/30
+    switch = tgen.add_switch("s5")
+    switch.add_link(tgen.gears["y2"])
+    switch.add_link(tgen.gears["y3"])
+
+    # 10.0.6.0/30
+    switch = tgen.add_switch("s6")
+    switch.add_link(tgen.gears["y2"])
+    switch.add_link(tgen.gears["z1"])
+
+    # 10.0.7.0/30
+    switch = tgen.add_switch("s7")
+    switch.add_link(tgen.gears["y3"])
+    switch.add_link(tgen.gears["z1"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_conditional_advertisement/test_bgp_conditional_advertisement.py b/tests/topotests/bgp_conditional_advertisement/test_bgp_conditional_advertisement.py
index 9e020ae86..02fcd5445 100644
--- a/tests/topotests/bgp_conditional_advertisement/test_bgp_conditional_advertisement.py
+++ b/tests/topotests/bgp_conditional_advertisement/test_bgp_conditional_advertisement.py
@@ -142,21 +142,18 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class BgpConditionalAdvertisementTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    r1 = tgen.add_router("r1")
+    r2 = tgen.add_router("r2")
+    r3 = tgen.add_router("r3")
 
-        r1 = tgen.add_router("r1")
-        r2 = tgen.add_router("r2")
-        r3 = tgen.add_router("r3")
+    switch = tgen.add_switch("s1")
+    switch.add_link(r1)
+    switch.add_link(r2)
 
-        switch = tgen.add_switch("s1")
-        switch.add_link(r1)
-        switch.add_link(r2)
-
-        switch = tgen.add_switch("s2")
-        switch.add_link(r2)
-        switch.add_link(r3)
+    switch = tgen.add_switch("s2")
+    switch.add_link(r2)
+    switch.add_link(r3)
 
 
 def setup_module(mod):
@@ -166,7 +163,7 @@ def setup_module(mod):
 
     logger.info("Running setup_module to create topology")
 
-    tgen = Topogen(BgpConditionalAdvertisementTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_default_afi_safi/test_bgp-default-afi-safi.py b/tests/topotests/bgp_default_afi_safi/test_bgp-default-afi-safi.py
index a22cd9406..4bcf2ebb4 100644
--- a/tests/topotests/bgp_default_afi_safi/test_bgp-default-afi-safi.py
+++ b/tests/topotests/bgp_default_afi_safi/test_bgp-default-afi-safi.py
@@ -50,22 +50,20 @@ from lib.common_config import step
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
 
-        for routern in range(1, 5):
-            tgen.add_router("r{}".format(routern))
+def build_topo(tgen):
+    for routern in range(1, 5):
+        tgen.add_router("r{}".format(routern))
 
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
-        switch.add_link(tgen.gears["r4"])
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
+    switch.add_link(tgen.gears["r4"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_default_route/test_bgp_default-originate.py b/tests/topotests/bgp_default_route/test_bgp_default-originate.py
index 68d9c52f4..9da8d0a49 100644
--- a/tests/topotests/bgp_default_route/test_bgp_default-originate.py
+++ b/tests/topotests/bgp_default_route/test_bgp_default-originate.py
@@ -41,20 +41,17 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    for routern in range(1, 3):
+        tgen.add_router("r{}".format(routern))
 
-        for routern in range(1, 3):
-            tgen.add_router("r{}".format(routern))
-
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_default_route_route_map_match/test_bgp_default-originate_route-map_match.py b/tests/topotests/bgp_default_route_route_map_match/test_bgp_default-originate_route-map_match.py
index 11a26570f..e6298dd78 100644
--- a/tests/topotests/bgp_default_route_route_map_match/test_bgp_default-originate_route-map_match.py
+++ b/tests/topotests/bgp_default_route_route_map_match/test_bgp_default-originate_route-map_match.py
@@ -41,20 +41,17 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    for routern in range(1, 3):
+        tgen.add_router("r{}".format(routern))
 
-        for routern in range(1, 3):
-            tgen.add_router("r{}".format(routern))
-
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_default_route_route_map_match2/test_bgp_default-originate_route-map_match2.py b/tests/topotests/bgp_default_route_route_map_match2/test_bgp_default-originate_route-map_match2.py
index f8c36f632..8f23cf25b 100644
--- a/tests/topotests/bgp_default_route_route_map_match2/test_bgp_default-originate_route-map_match2.py
+++ b/tests/topotests/bgp_default_route_route_map_match2/test_bgp_default-originate_route-map_match2.py
@@ -44,20 +44,17 @@ from lib.common_config import step
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    for routern in range(1, 3):
+        tgen.add_router("r{}".format(routern))
 
-        for routern in range(1, 3):
-            tgen.add_router("r{}".format(routern))
-
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_default_route_route_map_match_set/test_bgp_default-originate_route-map_match_set.py b/tests/topotests/bgp_default_route_route_map_match_set/test_bgp_default-originate_route-map_match_set.py
index 3735fcfb3..728819525 100644
--- a/tests/topotests/bgp_default_route_route_map_match_set/test_bgp_default-originate_route-map_match_set.py
+++ b/tests/topotests/bgp_default_route_route_map_match_set/test_bgp_default-originate_route-map_match_set.py
@@ -43,20 +43,17 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    for routern in range(1, 3):
+        tgen.add_router("r{}".format(routern))
 
-        for routern in range(1, 3):
-            tgen.add_router("r{}".format(routern))
-
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_default_route_route_map_set/test_bgp_default-originate_route-map_set.py b/tests/topotests/bgp_default_route_route_map_set/test_bgp_default-originate_route-map_set.py
index 05f14f352..4be98c08f 100644
--- a/tests/topotests/bgp_default_route_route_map_set/test_bgp_default-originate_route-map_set.py
+++ b/tests/topotests/bgp_default_route_route_map_set/test_bgp_default-originate_route-map_set.py
@@ -41,20 +41,17 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    for routern in range(1, 3):
+        tgen.add_router("r{}".format(routern))
 
-        for routern in range(1, 3):
-            tgen.add_router("r{}".format(routern))
-
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_disable_addpath_rx/r1/bgpd.conf b/tests/topotests/bgp_disable_addpath_rx/r1/bgpd.conf
index 1f3352131..af1353e0e 100644
--- a/tests/topotests/bgp_disable_addpath_rx/r1/bgpd.conf
+++ b/tests/topotests/bgp_disable_addpath_rx/r1/bgpd.conf
@@ -1,7 +1,9 @@
 !
 router bgp 65001
+ timers 3 10
  no bgp ebgp-requires-policy
  neighbor 192.168.1.2 remote-as external
+ neighbor 192.168.1.2 timers connect 5
  address-family ipv4 unicast
   neighbor 192.168.1.2 disable-addpath-rx
  exit-address-family
diff --git a/tests/topotests/bgp_disable_addpath_rx/r2/bgpd.conf b/tests/topotests/bgp_disable_addpath_rx/r2/bgpd.conf
index 92d95003e..db68e554d 100644
--- a/tests/topotests/bgp_disable_addpath_rx/r2/bgpd.conf
+++ b/tests/topotests/bgp_disable_addpath_rx/r2/bgpd.conf
@@ -1,8 +1,12 @@
 router bgp 65002
+ timers 3 10
  no bgp ebgp-requires-policy
  neighbor 192.168.1.1 remote-as external
+ neighbor 192.168.1.1 timers connect 5
  neighbor 192.168.2.3 remote-as external
+ neighbor 192.168.2.3 timers connect 5
  neighbor 192.168.2.4 remote-as external
+ neighbor 192.168.2.4 timers connect 5
  address-family ipv4 unicast
   neighbor 192.168.1.1 addpath-tx-all-paths
  exit-address-family
diff --git a/tests/topotests/bgp_disable_addpath_rx/r3/bgpd.conf b/tests/topotests/bgp_disable_addpath_rx/r3/bgpd.conf
index f5731a108..3ac6a08e4 100644
--- a/tests/topotests/bgp_disable_addpath_rx/r3/bgpd.conf
+++ b/tests/topotests/bgp_disable_addpath_rx/r3/bgpd.conf
@@ -1,6 +1,8 @@
 router bgp 65003
+ timers 3 10
  no bgp ebgp-requires-policy
  neighbor 192.168.2.2 remote-as external
+ neighbor 192.168.2.2 timers connect 5
  address-family ipv4 unicast
   redistribute connected
  exit-address-family
diff --git a/tests/topotests/bgp_disable_addpath_rx/r4/bgpd.conf b/tests/topotests/bgp_disable_addpath_rx/r4/bgpd.conf
index 527b8d348..8ab405fbd 100644
--- a/tests/topotests/bgp_disable_addpath_rx/r4/bgpd.conf
+++ b/tests/topotests/bgp_disable_addpath_rx/r4/bgpd.conf
@@ -1,6 +1,8 @@
 router bgp 65004
+ timers 3 10
  no bgp ebgp-requires-policy
  neighbor 192.168.2.2 remote-as external
+ neighbor 192.168.2.2 timers connect 5
  address-family ipv4 unicast
   redistribute connected
  exit-address-family
diff --git a/tests/topotests/bgp_disable_addpath_rx/test_disable_addpath_rx.py b/tests/topotests/bgp_disable_addpath_rx/test_disable_addpath_rx.py
index 2126d6226..ed88d5df2 100644
--- a/tests/topotests/bgp_disable_addpath_rx/test_disable_addpath_rx.py
+++ b/tests/topotests/bgp_disable_addpath_rx/test_disable_addpath_rx.py
@@ -25,7 +25,6 @@ Test if AddPath RX direction is not negotiated via AddPath capability.
 import os
 import sys
 import json
-import time
 import pytest
 import functools
 
@@ -35,32 +34,27 @@ sys.path.append(os.path.join(CWD, "../"))
 # pylint: disable=C0413
 from lib import topotest
 from lib.topogen import Topogen, TopoRouter, get_topogen
-from lib.topolog import logger
-from mininet.topo import Topo
 from lib.common_config import step
 
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    for routern in range(1, 5):
+        tgen.add_router("r{}".format(routern))
 
-        for routern in range(1, 5):
-            tgen.add_router("r{}".format(routern))
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
-
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
-        switch.add_link(tgen.gears["r4"])
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
+    switch.add_link(tgen.gears["r4"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_distance_change/test_bgp_distance_change.py b/tests/topotests/bgp_distance_change/test_bgp_distance_change.py
index 2583db01e..9af237986 100644
--- a/tests/topotests/bgp_distance_change/test_bgp_distance_change.py
+++ b/tests/topotests/bgp_distance_change/test_bgp_distance_change.py
@@ -52,20 +52,17 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    for routern in range(1, 3):
+        tgen.add_router("r{}".format(routern))
 
-        for routern in range(1, 3):
-            tgen.add_router("r{}".format(routern))
-
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_ebgp_common_subnet_nexthop_unchanged/test_bgp-ebgp-common-subnet-nexthop-unchanged.py b/tests/topotests/bgp_ebgp_common_subnet_nexthop_unchanged/test_bgp-ebgp-common-subnet-nexthop-unchanged.py
index 9460d6bae..c0886de85 100644
--- a/tests/topotests/bgp_ebgp_common_subnet_nexthop_unchanged/test_bgp-ebgp-common-subnet-nexthop-unchanged.py
+++ b/tests/topotests/bgp_ebgp_common_subnet_nexthop_unchanged/test_bgp-ebgp-common-subnet-nexthop-unchanged.py
@@ -54,21 +54,19 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
 
-        for routern in range(1, 4):
-            tgen.add_router("r{}".format(routern))
+def build_topo(tgen):
+    for routern in range(1, 4):
+        tgen.add_router("r{}".format(routern))
 
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_ebgp_requires_policy/test_bgp_ebgp_requires_policy.py b/tests/topotests/bgp_ebgp_requires_policy/test_bgp_ebgp_requires_policy.py
index 390c8b290..4f33e8124 100644
--- a/tests/topotests/bgp_ebgp_requires_policy/test_bgp_ebgp_requires_policy.py
+++ b/tests/topotests/bgp_ebgp_requires_policy/test_bgp_ebgp_requires_policy.py
@@ -60,31 +60,29 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
 
-        for routern in range(1, 7):
-            tgen.add_router("r{}".format(routern))
+def build_topo(tgen):
+    for routern in range(1, 7):
+        tgen.add_router("r{}".format(routern))
 
-        # Scenario 1.
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    # Scenario 1.
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
-        # Scenario 2.
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["r3"])
-        switch.add_link(tgen.gears["r4"])
+    # Scenario 2.
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r3"])
+    switch.add_link(tgen.gears["r4"])
 
-        # Scenario 3.
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["r5"])
-        switch.add_link(tgen.gears["r6"])
+    # Scenario 3.
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["r5"])
+    switch.add_link(tgen.gears["r6"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_ecmp_topo1/test_bgp_ecmp_topo1.py b/tests/topotests/bgp_ecmp_topo1/test_bgp_ecmp_topo1.py
index 841a76619..66714fd2f 100644
--- a/tests/topotests/bgp_ecmp_topo1/test_bgp_ecmp_topo1.py
+++ b/tests/topotests/bgp_ecmp_topo1/test_bgp_ecmp_topo1.py
@@ -58,32 +58,26 @@ total_ebgp_peers = 20
 #####################################################
 
 
-class BGPECMPTopo1(Topo):
-    "BGP ECMP Topology 1"
-
-    def build(self, **_opts):
-        tgen = get_topogen(self)
-
-        # Create the BGP router
-        router = tgen.add_router("r1")
-
-        # Setup Switches - 1 switch per 5 peering routers
-        for swNum in range(1, (total_ebgp_peers + 4) / 5 + 1):
-            switch = tgen.add_switch("s{}".format(swNum))
-            switch.add_link(router)
-
-        # Add 'total_ebgp_peers' number of eBGP ExaBGP neighbors
-        for peerNum in range(1, total_ebgp_peers + 1):
-            swNum = (peerNum - 1) / 5 + 1
-
-            peer_ip = "10.0.{}.{}".format(swNum, peerNum + 100)
-            peer_route = "via 10.0.{}.1".format(swNum)
-            peer = tgen.add_exabgp_peer(
-                "peer{}".format(peerNum), ip=peer_ip, defaultRoute=peer_route
-            )
+def build_topo(tgen):
+    router = tgen.add_router("r1")
+
+    # Setup Switches - 1 switch per 5 peering routers
+    for swNum in range(1, (total_ebgp_peers + 4) // 5 + 1):
+        switch = tgen.add_switch("s{}".format(swNum))
+        switch.add_link(router)
+
+    # Add 'total_ebgp_peers' number of eBGP ExaBGP neighbors
+    for peerNum in range(1, total_ebgp_peers + 1):
+        swNum = (peerNum - 1) // 5 + 1
+
+        peer_ip = "10.0.{}.{}".format(swNum, peerNum + 100)
+        peer_route = "via 10.0.{}.1".format(swNum)
+        peer = tgen.add_exabgp_peer(
+            "peer{}".format(peerNum), ip=peer_ip, defaultRoute=peer_route
+        )
 
-            switch = tgen.gears["s{}".format(swNum)]
-            switch.add_link(peer)
+        switch = tgen.gears["s{}".format(swNum)]
+        switch.add_link(peer)
 
 
 #####################################################
@@ -94,7 +88,7 @@ class BGPECMPTopo1(Topo):
 
 
 def setup_module(module):
-    tgen = Topogen(BGPECMPTopo1, module.__name__)
+    tgen = Topogen(build_topo, module.__name__)
     tgen.start_topology()
 
     # Starting Routers
diff --git a/tests/topotests/bgp_ecmp_topo2/test_ebgp_ecmp_topo2.py b/tests/topotests/bgp_ecmp_topo2/test_ebgp_ecmp_topo2.py
index 7bc3d2912..a82ed8ec8 100644
--- a/tests/topotests/bgp_ecmp_topo2/test_ebgp_ecmp_topo2.py
+++ b/tests/topotests/bgp_ecmp_topo2/test_ebgp_ecmp_topo2.py
@@ -71,14 +71,6 @@ from lib.topojson import build_topo_from_json, build_config_from_json
 pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
 
 
-# Reading the data from JSON File for topology and configuration creation
-jsonFile = "{}/ebgp_ecmp_topo2.json".format(CWD)
-
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 
 # Global variables
 NEXT_HOPS = {"ipv4": [], "ipv6": []}
@@ -89,21 +81,6 @@ NEXT_HOP_IP = {"ipv4": "10.0.0.1", "ipv6": "fd00::1"}
 BGP_CONVERGENCE = False
 
 
-class CreateTopo(Topo):
-    """
-    Test topology builder.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment.
@@ -125,7 +102,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/ebgp_ecmp_topo2.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
 
     # Starting topology, create tmp files which are loaded to routers
     #  to start deamons and then start routers
diff --git a/tests/topotests/bgp_ecmp_topo2/test_ibgp_ecmp_topo2.py b/tests/topotests/bgp_ecmp_topo2/test_ibgp_ecmp_topo2.py
index 15982dad5..561ba0edf 100644
--- a/tests/topotests/bgp_ecmp_topo2/test_ibgp_ecmp_topo2.py
+++ b/tests/topotests/bgp_ecmp_topo2/test_ibgp_ecmp_topo2.py
@@ -71,14 +71,6 @@ from lib.topojson import build_topo_from_json, build_config_from_json
 pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
 
 
-# Reading the data from JSON File for topology and configuration creation
-jsonFile = "{}/ibgp_ecmp_topo2.json".format(CWD)
-
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 
 # Global variables
 NEXT_HOPS = {"ipv4": [], "ipv6": []}
@@ -89,21 +81,6 @@ NEXT_HOP_IP = {"ipv4": "10.0.0.1", "ipv6": "fd00::1"}
 BGP_CONVERGENCE = False
 
 
-class CreateTopo(Topo):
-    """
-    Test topology builder.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment.
@@ -125,7 +102,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/ibgp_ecmp_topo2.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
 
     # Starting topology, create tmp files which are loaded to routers
     #  to start deamons and then start routers
diff --git a/tests/topotests/bgp_ecmp_topo3/test_ibgp_ecmp_topo3.py b/tests/topotests/bgp_ecmp_topo3/test_ibgp_ecmp_topo3.py
index 5f3ac4e71..66ebe5b58 100644
--- a/tests/topotests/bgp_ecmp_topo3/test_ibgp_ecmp_topo3.py
+++ b/tests/topotests/bgp_ecmp_topo3/test_ibgp_ecmp_topo3.py
@@ -40,7 +40,7 @@ sys.path.append(os.path.join(CWD, "../../"))
 # pylint: disable=C0413
 # Import topogen and topotest helpers
 from lib.topogen import Topogen, get_topogen
-from mininet.topo import Topo
+from lib import topojson
 
 from lib.common_config import (
     start_topology,
@@ -63,15 +63,6 @@ from lib.topojson import build_topo_from_json, build_config_from_json
 pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
 
 
-# Reading the data from JSON File for topology and configuration creation
-jsonFile = "{}/ibgp_ecmp_topo3.json".format(CWD)
-
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
-
 # Global variables
 NEXT_HOPS = {"ipv4": [], "ipv6": []}
 NETWORK = {"ipv4": "192.168.1.10/32", "ipv6": "fd00:0:0:1::10/128"}
@@ -79,45 +70,20 @@ NEXT_HOP_IP = {"ipv4": "10.0.0.1", "ipv6": "fd00::1"}
 BGP_CONVERGENCE = False
 
 
-class CreateTopo(Topo):
-    """
-    Test topology builder.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment.
 
     * `mod`: module name
     """
-    global NEXT_HOPS, INTF_LIST_R3, INTF_LIST_R2, TEST_STATIC
     global ADDR_TYPES
 
     testsuite_run_time = time.asctime(time.localtime(time.time()))
     logger.info("Testsuite start time: {}".format(testsuite_run_time))
     logger.info("=" * 40)
 
-    logger.info("Running setup_module to create topology")
-
-    # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
-
-    # Starting topology, create tmp files which are loaded to routers
-    #  to start deamons and then start routers
-    start_topology(tgen)
-
-    # Creating configuration from JSON
-    build_config_from_json(tgen, topo)
+    tgen = topojson.setup_module_from_json(mod.__file__)
+    topo = tgen.json_topo
 
     # Don't run this test if we have any failure.
     if tgen.routers_have_failure():
@@ -136,18 +102,7 @@ def setup_module(mod):
 
 
 def teardown_module():
-    """
-    Teardown the pytest environment.
-
-    * `mod`: module name
-    """
-
-    logger.info("Running teardown_module to delete topology")
-
-    tgen = get_topogen()
-
-    # Stop toplogy and Remove tmp files
-    tgen.stop_topology()
+    get_topogen().stop_topology()
 
 
 def static_or_nw(tgen, topo, tc_name, test_type, dut):
@@ -221,12 +176,11 @@ def static_or_nw(tgen, topo, tc_name, test_type, dut):
 
 
 @pytest.mark.parametrize("test_type", ["redist_static"])
-def test_ecmp_fast_convergence(request, test_type):
+def test_ecmp_fast_convergence(request, test_type, tgen, topo):
     """This test is to verify bgp fast-convergence cli functionality"""
 
     tc_name = request.node.name
     write_test_header(tc_name)
-    tgen = get_topogen()
 
     # Verifying RIB routes
     dut = "r3"
diff --git a/tests/topotests/bgp_evpn_mh/test_evpn_mh.py b/tests/topotests/bgp_evpn_mh/test_evpn_mh.py
index 8cdf3529d..bad4da116 100644
--- a/tests/topotests/bgp_evpn_mh/test_evpn_mh.py
+++ b/tests/topotests/bgp_evpn_mh/test_evpn_mh.py
@@ -62,7 +62,7 @@ pytestmark = [pytest.mark.bgpd, pytest.mark.pimd]
 #####################################################
 
 
-class NetworkTopo(Topo):
+def build_topo(tgen):
     """
     EVPN Multihoming Topology -
     1. Two level CLOS
@@ -71,110 +71,105 @@ class NetworkTopo(Topo):
     4. Two dual attached hosts per-rack - hostdx1, hostdx2
     """
 
-    def build(self, **_opts):
-        "Build function"
-
-        tgen = get_topogen(self)
-
-        tgen.add_router("spine1")
-        tgen.add_router("spine2")
-        tgen.add_router("torm11")
-        tgen.add_router("torm12")
-        tgen.add_router("torm21")
-        tgen.add_router("torm22")
-        tgen.add_router("hostd11")
-        tgen.add_router("hostd12")
-        tgen.add_router("hostd21")
-        tgen.add_router("hostd22")
-
-        # On main router
-        # First switch is for a dummy interface (for local network)
-
-        ##################### spine1 ########################
-        # spine1-eth0 is connected to torm11-eth0
-        switch = tgen.add_switch("sw1")
-        switch.add_link(tgen.gears["spine1"])
-        switch.add_link(tgen.gears["torm11"])
-
-        # spine1-eth1 is connected to torm12-eth0
-        switch = tgen.add_switch("sw2")
-        switch.add_link(tgen.gears["spine1"])
-        switch.add_link(tgen.gears["torm12"])
-
-        # spine1-eth2 is connected to torm21-eth0
-        switch = tgen.add_switch("sw3")
-        switch.add_link(tgen.gears["spine1"])
-        switch.add_link(tgen.gears["torm21"])
-
-        # spine1-eth3 is connected to torm22-eth0
-        switch = tgen.add_switch("sw4")
-        switch.add_link(tgen.gears["spine1"])
-        switch.add_link(tgen.gears["torm22"])
-
-        ##################### spine2 ########################
-        # spine2-eth0 is connected to torm11-eth1
-        switch = tgen.add_switch("sw5")
-        switch.add_link(tgen.gears["spine2"])
-        switch.add_link(tgen.gears["torm11"])
-
-        # spine2-eth1 is connected to torm12-eth1
-        switch = tgen.add_switch("sw6")
-        switch.add_link(tgen.gears["spine2"])
-        switch.add_link(tgen.gears["torm12"])
-
-        # spine2-eth2 is connected to torm21-eth1
-        switch = tgen.add_switch("sw7")
-        switch.add_link(tgen.gears["spine2"])
-        switch.add_link(tgen.gears["torm21"])
-
-        # spine2-eth3 is connected to torm22-eth1
-        switch = tgen.add_switch("sw8")
-        switch.add_link(tgen.gears["spine2"])
-        switch.add_link(tgen.gears["torm22"])
-
-        ##################### torm11 ########################
-        # torm11-eth2 is connected to hostd11-eth0
-        switch = tgen.add_switch("sw9")
-        switch.add_link(tgen.gears["torm11"])
-        switch.add_link(tgen.gears["hostd11"])
-
-        # torm11-eth3 is connected to hostd12-eth0
-        switch = tgen.add_switch("sw10")
-        switch.add_link(tgen.gears["torm11"])
-        switch.add_link(tgen.gears["hostd12"])
-
-        ##################### torm12 ########################
-        # torm12-eth2 is connected to hostd11-eth1
-        switch = tgen.add_switch("sw11")
-        switch.add_link(tgen.gears["torm12"])
-        switch.add_link(tgen.gears["hostd11"])
-
-        # torm12-eth3 is connected to hostd12-eth1
-        switch = tgen.add_switch("sw12")
-        switch.add_link(tgen.gears["torm12"])
-        switch.add_link(tgen.gears["hostd12"])
-
-        ##################### torm21 ########################
-        # torm21-eth2 is connected to hostd21-eth0
-        switch = tgen.add_switch("sw13")
-        switch.add_link(tgen.gears["torm21"])
-        switch.add_link(tgen.gears["hostd21"])
-
-        # torm21-eth3 is connected to hostd22-eth0
-        switch = tgen.add_switch("sw14")
-        switch.add_link(tgen.gears["torm21"])
-        switch.add_link(tgen.gears["hostd22"])
-
-        ##################### torm22 ########################
-        # torm22-eth2 is connected to hostd21-eth1
-        switch = tgen.add_switch("sw15")
-        switch.add_link(tgen.gears["torm22"])
-        switch.add_link(tgen.gears["hostd21"])
-
-        # torm22-eth3 is connected to hostd22-eth1
-        switch = tgen.add_switch("sw16")
-        switch.add_link(tgen.gears["torm22"])
-        switch.add_link(tgen.gears["hostd22"])
+    tgen.add_router("spine1")
+    tgen.add_router("spine2")
+    tgen.add_router("torm11")
+    tgen.add_router("torm12")
+    tgen.add_router("torm21")
+    tgen.add_router("torm22")
+    tgen.add_router("hostd11")
+    tgen.add_router("hostd12")
+    tgen.add_router("hostd21")
+    tgen.add_router("hostd22")
+
+    # On main router
+    # First switch is for a dummy interface (for local network)
+
+    ##################### spine1 ########################
+    # spine1-eth0 is connected to torm11-eth0
+    switch = tgen.add_switch("sw1")
+    switch.add_link(tgen.gears["spine1"])
+    switch.add_link(tgen.gears["torm11"])
+
+    # spine1-eth1 is connected to torm12-eth0
+    switch = tgen.add_switch("sw2")
+    switch.add_link(tgen.gears["spine1"])
+    switch.add_link(tgen.gears["torm12"])
+
+    # spine1-eth2 is connected to torm21-eth0
+    switch = tgen.add_switch("sw3")
+    switch.add_link(tgen.gears["spine1"])
+    switch.add_link(tgen.gears["torm21"])
+
+    # spine1-eth3 is connected to torm22-eth0
+    switch = tgen.add_switch("sw4")
+    switch.add_link(tgen.gears["spine1"])
+    switch.add_link(tgen.gears["torm22"])
+
+    ##################### spine2 ########################
+    # spine2-eth0 is connected to torm11-eth1
+    switch = tgen.add_switch("sw5")
+    switch.add_link(tgen.gears["spine2"])
+    switch.add_link(tgen.gears["torm11"])
+
+    # spine2-eth1 is connected to torm12-eth1
+    switch = tgen.add_switch("sw6")
+    switch.add_link(tgen.gears["spine2"])
+    switch.add_link(tgen.gears["torm12"])
+
+    # spine2-eth2 is connected to torm21-eth1
+    switch = tgen.add_switch("sw7")
+    switch.add_link(tgen.gears["spine2"])
+    switch.add_link(tgen.gears["torm21"])
+
+    # spine2-eth3 is connected to torm22-eth1
+    switch = tgen.add_switch("sw8")
+    switch.add_link(tgen.gears["spine2"])
+    switch.add_link(tgen.gears["torm22"])
+
+    ##################### torm11 ########################
+    # torm11-eth2 is connected to hostd11-eth0
+    switch = tgen.add_switch("sw9")
+    switch.add_link(tgen.gears["torm11"])
+    switch.add_link(tgen.gears["hostd11"])
+
+    # torm11-eth3 is connected to hostd12-eth0
+    switch = tgen.add_switch("sw10")
+    switch.add_link(tgen.gears["torm11"])
+    switch.add_link(tgen.gears["hostd12"])
+
+    ##################### torm12 ########################
+    # torm12-eth2 is connected to hostd11-eth1
+    switch = tgen.add_switch("sw11")
+    switch.add_link(tgen.gears["torm12"])
+    switch.add_link(tgen.gears["hostd11"])
+
+    # torm12-eth3 is connected to hostd12-eth1
+    switch = tgen.add_switch("sw12")
+    switch.add_link(tgen.gears["torm12"])
+    switch.add_link(tgen.gears["hostd12"])
+
+    ##################### torm21 ########################
+    # torm21-eth2 is connected to hostd21-eth0
+    switch = tgen.add_switch("sw13")
+    switch.add_link(tgen.gears["torm21"])
+    switch.add_link(tgen.gears["hostd21"])
+
+    # torm21-eth3 is connected to hostd22-eth0
+    switch = tgen.add_switch("sw14")
+    switch.add_link(tgen.gears["torm21"])
+    switch.add_link(tgen.gears["hostd22"])
+
+    ##################### torm22 ########################
+    # torm22-eth2 is connected to hostd21-eth1
+    switch = tgen.add_switch("sw15")
+    switch.add_link(tgen.gears["torm22"])
+    switch.add_link(tgen.gears["hostd21"])
+
+    # torm22-eth3 is connected to hostd22-eth1
+    switch = tgen.add_switch("sw16")
+    switch.add_link(tgen.gears["torm22"])
+    switch.add_link(tgen.gears["hostd22"])
 
 
 #####################################################
@@ -371,7 +366,7 @@ def config_hosts(tgen, hosts):
 
 def setup_module(module):
     "Setup topology"
-    tgen = Topogen(NetworkTopo, module.__name__)
+    tgen = Topogen(build_topo, module.__name__)
     tgen.start_topology()
 
     krel = platform.release()
diff --git a/tests/topotests/bgp_evpn_overlay_index_gateway/test_bgp_evpn_overlay_index_gateway.py b/tests/topotests/bgp_evpn_overlay_index_gateway/test_bgp_evpn_overlay_index_gateway.py
index 7a53173dc..20459adbd 100755
--- a/tests/topotests/bgp_evpn_overlay_index_gateway/test_bgp_evpn_overlay_index_gateway.py
+++ b/tests/topotests/bgp_evpn_overlay_index_gateway/test_bgp_evpn_overlay_index_gateway.py
@@ -88,29 +88,23 @@ HOST_SUFFIX = {'host1': '1', 'host2': '2'}
 TRIGGERS = ["base", "no_rt5", "no_rt2"]
 
 
-class TemplateTopo(Topo):
-    """Test topology builder"""
+def build_topo(tgen):
+    # This function only purpose is to define allocation and relationship
+    # between routers and add links.
 
-    def build(self, *_args, **_opts):
-        """Build function"""
-        tgen = get_topogen(self)
+    # Create routers
+    for pe in PES:
+        tgen.add_router(pe)
+    for host in HOSTS:
+        tgen.add_router(host)
 
-        # This function only purpose is to define allocation and relationship
-        # between routers and add links.
+    krel = platform.release()
+    logger.info('Kernel version ' + krel)
 
-        # Create routers
-        for pe in PES:
-            tgen.add_router(pe)
-        for host in HOSTS:
-            tgen.add_router(host)
-
-        krel = platform.release()
-        logger.info('Kernel version ' + krel)
-
-        #Add links
-        tgen.add_link(tgen.gears['PE1'], tgen.gears['PE2'], 'PE1-eth0', 'PE2-eth0')
-        tgen.add_link(tgen.gears['PE1'], tgen.gears['host1'], 'PE1-eth1', 'host1-eth0')
-        tgen.add_link(tgen.gears['PE2'], tgen.gears['host2'], 'PE2-eth1', 'host2-eth0')
+    #Add links
+    tgen.add_link(tgen.gears['PE1'], tgen.gears['PE2'], 'PE1-eth0', 'PE2-eth0')
+    tgen.add_link(tgen.gears['PE1'], tgen.gears['host1'], 'PE1-eth1', 'host1-eth0')
+    tgen.add_link(tgen.gears['PE2'], tgen.gears['host2'], 'PE2-eth1', 'host2-eth0')
 
 
 def setup_module(mod):
@@ -123,7 +117,7 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     # ... and here it calls Mininet initialization functions.
 
     kernelv = platform.release()
diff --git a/tests/topotests/bgp_evpn_rt5/test_bgp_evpn.py b/tests/topotests/bgp_evpn_rt5/test_bgp_evpn.py
index 02e67b70c..98411938c 100644
--- a/tests/topotests/bgp_evpn_rt5/test_bgp_evpn.py
+++ b/tests/topotests/bgp_evpn_rt5/test_bgp_evpn.py
@@ -48,31 +48,28 @@ from lib.micronet_compat import Topo
 
 pytestmark = [pytest.mark.bgpd]
 
-class BGPEVPNTopo(Topo):
-    "Test topology builder"
 
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    "Build function"
 
-        tgen.add_router("r1")
-        tgen.add_router("r2")
+    tgen.add_router("r1")
+    tgen.add_router("r2")
 
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["r1"])
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r1"])
 
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["r2"])
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
 
-    tgen = Topogen(BGPEVPNTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_evpn_vxlan_topo1/test_bgp_evpn_vxlan.py b/tests/topotests/bgp_evpn_vxlan_topo1/test_bgp_evpn_vxlan.py
index 0380ac07d..d300561e1 100755
--- a/tests/topotests/bgp_evpn_vxlan_topo1/test_bgp_evpn_vxlan.py
+++ b/tests/topotests/bgp_evpn_vxlan_topo1/test_bgp_evpn_vxlan.py
@@ -49,49 +49,45 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd, pytest.mark.ospfd]
 
 
-class TemplateTopo(Topo):
-    "Test topology builder"
-
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
-
-        # This function only purpose is to define allocation and relationship
-        # between routers, switches and hosts.
-        #
-        #
-        # Create routers
-        tgen.add_router("P1")
-        tgen.add_router("PE1")
-        tgen.add_router("PE2")
-        tgen.add_router("host1")
-        tgen.add_router("host2")
-
-        # Host1-PE1
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["host1"])
-        switch.add_link(tgen.gears["PE1"])
-
-        # PE1-P1
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["PE1"])
-        switch.add_link(tgen.gears["P1"])
-
-        # P1-PE2
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["P1"])
-        switch.add_link(tgen.gears["PE2"])
-
-        # PE2-host2
-        switch = tgen.add_switch("s4")
-        switch.add_link(tgen.gears["PE2"])
-        switch.add_link(tgen.gears["host2"])
+def build_topo(tgen):
+    "Build function"
+
+    # This function only purpose is to define allocation and relationship
+    # between routers, switches and hosts.
+    #
+    #
+    # Create routers
+    tgen.add_router("P1")
+    tgen.add_router("PE1")
+    tgen.add_router("PE2")
+    tgen.add_router("host1")
+    tgen.add_router("host2")
+
+    # Host1-PE1
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["host1"])
+    switch.add_link(tgen.gears["PE1"])
+
+    # PE1-P1
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["PE1"])
+    switch.add_link(tgen.gears["P1"])
+
+    # P1-PE2
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["P1"])
+    switch.add_link(tgen.gears["PE2"])
+
+    # PE2-host2
+    switch = tgen.add_switch("s4")
+    switch.add_link(tgen.gears["PE2"])
+    switch.add_link(tgen.gears["host2"])
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     # ... and here it calls Mininet initialization functions.
     tgen.start_topology()
 
diff --git a/tests/topotests/bgp_features/test_bgp_features.py b/tests/topotests/bgp_features/test_bgp_features.py
index 54f61f92e..f2e09fb01 100644
--- a/tests/topotests/bgp_features/test_bgp_features.py
+++ b/tests/topotests/bgp_features/test_bgp_features.py
@@ -56,40 +56,48 @@ pytestmark = [pytest.mark.bgpd, pytest.mark.ospfd]
 #####################################################
 
 
-class BGPFeaturesTopo1(Topo):
-    "BGP Features Topology 1"
-
-    def build(self, **_opts):
-        tgen = get_topogen(self)
-
-        # Create the routers
-        for rtrNum in range(1, 6):
-            tgen.add_router("r{}".format(rtrNum))
-
-        # Setup Switches and connections
-        for swNum in range(1, 11):
-            tgen.add_switch("sw{}".format(swNum))
-
-        # Add connections to stub switches
-        tgen.gears["r1"].add_link(tgen.gears["sw6"])
-        tgen.gears["r2"].add_link(tgen.gears["sw7"])
-        tgen.gears["r3"].add_link(tgen.gears["sw8"])
-        tgen.gears["r4"].add_link(tgen.gears["sw9"])
-        tgen.gears["r5"].add_link(tgen.gears["sw10"])
-
-        # Add connections to R1-R2-R3 core
-        tgen.gears["r1"].add_link(tgen.gears["sw1"])
-        tgen.gears["r1"].add_link(tgen.gears["sw3"])
-        tgen.gears["r2"].add_link(tgen.gears["sw1"])
-        tgen.gears["r2"].add_link(tgen.gears["sw2"])
-        tgen.gears["r3"].add_link(tgen.gears["sw2"])
-        tgen.gears["r3"].add_link(tgen.gears["sw3"])
-
-        # Add connections to external R4/R5 Routers
-        tgen.gears["r1"].add_link(tgen.gears["sw4"])
-        tgen.gears["r4"].add_link(tgen.gears["sw4"])
-        tgen.gears["r2"].add_link(tgen.gears["sw5"])
-        tgen.gears["r5"].add_link(tgen.gears["sw5"])
+def build_topo(tgen):
+    for rtrNum in range(1, 6):
+        tgen.add_router("r{}".format(rtrNum))
+
+    # create ExaBGP peers
+    for peer_num in range(1, 5):
+        tgen.add_exabgp_peer(
+            "peer{}".format(peer_num),
+            ip="192.168.101.{}".format(peer_num + 2),
+            defaultRoute="via 192.168.101.1",
+        )
+
+    # Setup Switches and connections
+    for swNum in range(1, 11):
+        tgen.add_switch("sw{}".format(swNum))
+
+    # Add connections to stub switches
+    tgen.gears["r1"].add_link(tgen.gears["sw6"])
+    tgen.gears["r2"].add_link(tgen.gears["sw7"])
+    tgen.gears["r3"].add_link(tgen.gears["sw8"])
+    tgen.gears["r4"].add_link(tgen.gears["sw9"])
+    tgen.gears["r5"].add_link(tgen.gears["sw10"])
+
+    # Add connections to R1-R2-R3 core
+    tgen.gears["r1"].add_link(tgen.gears["sw1"])
+    tgen.gears["r1"].add_link(tgen.gears["sw3"])
+    tgen.gears["r2"].add_link(tgen.gears["sw1"])
+    tgen.gears["r2"].add_link(tgen.gears["sw2"])
+    tgen.gears["r3"].add_link(tgen.gears["sw2"])
+    tgen.gears["r3"].add_link(tgen.gears["sw3"])
+
+    # Add connections to external R4/R5 Routers
+    tgen.gears["r1"].add_link(tgen.gears["sw4"])
+    tgen.gears["r4"].add_link(tgen.gears["sw4"])
+    tgen.gears["r2"].add_link(tgen.gears["sw5"])
+    tgen.gears["r5"].add_link(tgen.gears["sw5"])
+
+    # Add ExaBGP peers to sw4
+    tgen.gears["peer1"].add_link(tgen.gears["sw4"])
+    tgen.gears["peer2"].add_link(tgen.gears["sw4"])
+    tgen.gears["peer3"].add_link(tgen.gears["sw4"])
+    tgen.gears["peer4"].add_link(tgen.gears["sw4"])
 
 
 #####################################################
@@ -100,7 +108,7 @@ class BGPFeaturesTopo1(Topo):
 
 
 def setup_module(module):
-    tgen = Topogen(BGPFeaturesTopo1, module.__name__)
+    tgen = Topogen(build_topo, module.__name__)
     tgen.start_topology()
 
     # Starting Routers
diff --git a/tests/topotests/bgp_flowspec/test_bgp_flowspec_topo.py b/tests/topotests/bgp_flowspec/test_bgp_flowspec_topo.py
index 6a12ed80d..05ea944eb 100644
--- a/tests/topotests/bgp_flowspec/test_bgp_flowspec_topo.py
+++ b/tests/topotests/bgp_flowspec/test_bgp_flowspec_topo.py
@@ -82,24 +82,18 @@ pytestmark = [pytest.mark.bgpd]
 #####################################################
 
 
-class BGPFLOWSPECTopo1(Topo):
-    "BGP EBGP Flowspec Topology 1"
+def build_topo(tgen):
+    tgen.add_router("r1")
 
-    def build(self, **_opts):
-        tgen = get_topogen(self)
+    # Setup Control Path Switch 1. r1-eth0
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
 
-        # Setup Routers
-        tgen.add_router("r1")
-
-        # Setup Control Path Switch 1. r1-eth0
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-
-        ## Add eBGP ExaBGP neighbors
-        peer_ip = "10.0.1.101"  ## peer
-        peer_route = "via 10.0.1.1"  ## router
-        peer = tgen.add_exabgp_peer("peer1", ip=peer_ip, defaultRoute=peer_route)
-        switch.add_link(peer)
+    ## Add eBGP ExaBGP neighbors
+    peer_ip = "10.0.1.101"  ## peer
+    peer_route = "via 10.0.1.1"  ## router
+    peer = tgen.add_exabgp_peer("peer1", ip=peer_ip, defaultRoute=peer_route)
+    switch.add_link(peer)
 
 
 #####################################################
@@ -110,7 +104,7 @@ class BGPFLOWSPECTopo1(Topo):
 
 
 def setup_module(module):
-    tgen = Topogen(BGPFLOWSPECTopo1, module.__name__)
+    tgen = Topogen(build_topo, module.__name__)
 
     tgen.start_topology()
     # check for zebra capability
diff --git a/tests/topotests/bgp_gr_functionality_topo1/test_bgp_gr_functionality_topo1.py b/tests/topotests/bgp_gr_functionality_topo1/test_bgp_gr_functionality_topo1.py
index bd3f6209a..4ee3b9708 100644
--- a/tests/topotests/bgp_gr_functionality_topo1/test_bgp_gr_functionality_topo1.py
+++ b/tests/topotests/bgp_gr_functionality_topo1/test_bgp_gr_functionality_topo1.py
@@ -142,15 +142,6 @@ from lib.common_config import (
 pytestmark = [pytest.mark.bgpd]
 
 
-# Reading the data from JSON File for topology and configuration creation
-jsonFile = "{}/bgp_gr_topojson_topo1.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    logger.info("Could not read file:", jsonFile)
-
-
 # Global variables
 NEXT_HOP_IP = {"ipv4": "192.168.1.10", "ipv6": "fd00:0:0:1::10"}
 NEXT_HOP_IP_1 = {"ipv4": "192.168.0.1", "ipv6": "fd00::1"}
@@ -160,28 +151,6 @@ GR_RESTART_TIMER = 20
 PREFERRED_NEXT_HOP = "link_local"
 
 
-class GenerateTopo(Topo):
-    """
-    Test topology builder
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
-
-        # This function only purpose is to create topology
-        # as defined in input json file.
-        #
-        # Create topology (setup module)
-        # Creating 2 routers topology, r1, r2in IBGP
-        # Bring up topology
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
@@ -203,7 +172,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(GenerateTopo, mod.__name__)
+    json_file = "{}/bgp_gr_topojson_topo1.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/bgp_gr_functionality_topo2/test_bgp_gr_functionality_topo2.py b/tests/topotests/bgp_gr_functionality_topo2/test_bgp_gr_functionality_topo2.py
index dd44cbf96..5fc361f8f 100644
--- a/tests/topotests/bgp_gr_functionality_topo2/test_bgp_gr_functionality_topo2.py
+++ b/tests/topotests/bgp_gr_functionality_topo2/test_bgp_gr_functionality_topo2.py
@@ -141,14 +141,6 @@ from lib.common_config import (
 pytestmark = [pytest.mark.bgpd]
 
 
-# Reading the data from JSON File for topology and configuration creation
-jsonFile = "{}/bgp_gr_topojson_topo2.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    logger.info("Could not read file:", jsonFile)
-
 # Global variables
 BGP_CONVERGENCE = False
 GR_RESTART_TIMER = 5
@@ -159,28 +151,6 @@ NEXT_HOP_4 = ["192.168.1.1", "192.168.4.2"]
 NEXT_HOP_6 = ["fd00:0:0:1::1", "fd00:0:0:4::2"]
 
 
-class GenerateTopo(Topo):
-    """
-    Test topology builder
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
-
-        # This function only purpose is to create topology
-        # as defined in input json file.
-        #
-        # Create topology (setup module)
-        # Creating 2 routers topology, r1, r2in IBGP
-        # Bring up topology
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
@@ -202,7 +172,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(GenerateTopo, mod.__name__)
+    json_file = "{}/bgp_gr_topojson_topo2.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/bgp_gshut/test_bgp_gshut.py b/tests/topotests/bgp_gshut/test_bgp_gshut.py
index d32ba1c1f..a08f74d6c 100644
--- a/tests/topotests/bgp_gshut/test_bgp_gshut.py
+++ b/tests/topotests/bgp_gshut/test_bgp_gshut.py
@@ -78,28 +78,25 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    for routern in range(1, 6):
+        tgen.add_router("r{}".format(routern))
 
-        for routern in range(1, 6):
-            tgen.add_router("r{}".format(routern))
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
 
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r4"])
 
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r4"])
-
-        switch = tgen.add_switch("s4")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r5"])
+    switch = tgen.add_switch("s4")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r5"])
 
 
 def _run_cmd_and_check(router, cmd, results_file, retries=100, intvl=0.5):
@@ -110,7 +107,7 @@ def _run_cmd_and_check(router, cmd, results_file, retries=100, intvl=0.5):
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_gshut_topo1/test_ebgp_gshut_topo1.py b/tests/topotests/bgp_gshut_topo1/test_ebgp_gshut_topo1.py
index 2595b2099..2bddd9c77 100644
--- a/tests/topotests/bgp_gshut_topo1/test_ebgp_gshut_topo1.py
+++ b/tests/topotests/bgp_gshut_topo1/test_ebgp_gshut_topo1.py
@@ -75,16 +75,9 @@ from lib.bgp import (
 )
 from lib.topojson import build_topo_from_json, build_config_from_json
 
-pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
 
+pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
 
-# Reading the data from JSON File for topology and configuration creation
-jsonFile = "{}/ebgp_gshut_topo1.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    logger.info("Could not read file:", jsonFile)
 
 # Global variables
 NETWORK = {"ipv4": "100.0.10.1/32", "ipv6": "1::1/128"}
@@ -94,28 +87,6 @@ PREFERRED_NEXT_HOP = "link_local"
 BGP_CONVERGENCE = False
 
 
-class GenerateTopo(Topo):
-    """
-    Test topology builder
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
-
-        # This function only purpose is to create topology
-        # as defined in input json file.
-        #
-        # Create topology (setup module)
-        # Creating 2 routers topology, r1, r2in IBGP
-        # Bring up topology
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
@@ -137,7 +108,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(GenerateTopo, mod.__name__)
+    json_file = "{}/ebgp_gshut_topo1.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/bgp_gshut_topo1/test_ibgp_gshut_topo1.py b/tests/topotests/bgp_gshut_topo1/test_ibgp_gshut_topo1.py
index 3f3354dc8..90d285f0f 100644
--- a/tests/topotests/bgp_gshut_topo1/test_ibgp_gshut_topo1.py
+++ b/tests/topotests/bgp_gshut_topo1/test_ibgp_gshut_topo1.py
@@ -78,14 +78,6 @@ from lib.topojson import build_topo_from_json, build_config_from_json
 pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
 
 
-# Reading the data from JSON File for topology and configuration creation
-jsonFile = "{}/ibgp_gshut_topo1.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    logger.info("Could not read file:", jsonFile)
-
 # Global variables
 NETWORK = {"ipv4": "100.0.10.1/32", "ipv6": "1::1/128"}
 NEXT_HOP_IP_1 = {"ipv4": "10.0.3.1", "ipv6": "fd00:0:0:3::1"}
@@ -94,28 +86,6 @@ PREFERRED_NEXT_HOP = "link_local"
 BGP_CONVERGENCE = False
 
 
-class GenerateTopo(Topo):
-    """
-    Test topology builder
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
-
-        # This function only purpose is to create topology
-        # as defined in input json file.
-        #
-        # Create topology (setup module)
-        # Creating 2 routers topology, r1, r2in IBGP
-        # Bring up topology
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
@@ -137,7 +107,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(GenerateTopo, mod.__name__)
+    json_file = "{}/ibgp_gshut_topo1.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/bgp_ipv4_over_ipv6/test_rfc5549_ebgp_ibgp_nbr.py b/tests/topotests/bgp_ipv4_over_ipv6/test_rfc5549_ebgp_ibgp_nbr.py
index 4f72cbb30..04945a94a 100644
--- a/tests/topotests/bgp_ipv4_over_ipv6/test_rfc5549_ebgp_ibgp_nbr.py
+++ b/tests/topotests/bgp_ipv4_over_ipv6/test_rfc5549_ebgp_ibgp_nbr.py
@@ -39,7 +39,6 @@ sys.path.append(os.path.join(CWD, "../../"))
 # pylint: disable=C0413
 # Import topogen and topotest helpers
 from lib.topogen import Topogen, get_topogen
-from mininet.topo import Topo
 
 from lib.common_config import (
     start_topology,
@@ -66,13 +65,6 @@ from lib.topojson import build_topo_from_json, build_config_from_json
 
 # Global variables
 topo = None
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/rfc5549_ebgp_ibgp_nbr.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 
 # Global variables
 NETWORK = {
@@ -121,21 +113,6 @@ unchange is configure on EBGP peers
  """
 
 
-class CreateTopo(Topo):
-    """
-    Test topology builder.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """Set up the pytest environment."""
 
@@ -147,7 +124,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/rfc5549_ebgp_ibgp_nbr.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
 
     # Starting topology, create tmp files which are loaded to routers
     #  to start deamons and then start routers
diff --git a/tests/topotests/bgp_ipv4_over_ipv6/test_rfc5549_ebgp_nbr.py b/tests/topotests/bgp_ipv4_over_ipv6/test_rfc5549_ebgp_nbr.py
index 12237fec6..f09da23bc 100644
--- a/tests/topotests/bgp_ipv4_over_ipv6/test_rfc5549_ebgp_nbr.py
+++ b/tests/topotests/bgp_ipv4_over_ipv6/test_rfc5549_ebgp_nbr.py
@@ -40,7 +40,6 @@ sys.path.append(os.path.join(CWD, "../../"))
 # pylint: disable=C0413
 # Import topogen and topotest helpers
 from lib.topogen import Topogen, get_topogen
-from mininet.topo import Topo
 
 from lib.common_config import (
     start_topology,
@@ -71,13 +70,6 @@ from lib.topojson import build_topo_from_json, build_config_from_json
 
 # Global variables
 topo = None
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/rfc5549_ebgp_nbr.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 
 # Global variables
 NETWORK = {
@@ -137,21 +129,6 @@ TC32. Verify IPv4 route received with IPv6 nexthop can be advertised to
  """
 
 
-class CreateTopo(Topo):
-    """
-    Test topology builder.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """Set up the pytest environment."""
     global topo, ADDR_TYPES
@@ -163,7 +140,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/rfc5549_ebgp_nbr.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
 
     # Starting topology, create tmp files which are loaded to routers
     #  to start deamons and then start routers
diff --git a/tests/topotests/bgp_ipv4_over_ipv6/test_rfc5549_ebgp_unnumbered_nbr.py b/tests/topotests/bgp_ipv4_over_ipv6/test_rfc5549_ebgp_unnumbered_nbr.py
index 2675f3a39..5966ffded 100644
--- a/tests/topotests/bgp_ipv4_over_ipv6/test_rfc5549_ebgp_unnumbered_nbr.py
+++ b/tests/topotests/bgp_ipv4_over_ipv6/test_rfc5549_ebgp_unnumbered_nbr.py
@@ -37,7 +37,6 @@ sys.path.append(os.path.join(CWD, "../"))
 sys.path.append(os.path.join(CWD, "../../"))
 
 from lib.topogen import Topogen, get_topogen
-from mininet.topo import Topo
 
 from lib.common_config import (
     write_test_header,
@@ -62,13 +61,6 @@ from lib.topojson import build_topo_from_json, build_config_from_json
 
 # Global variables
 topo = None
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/rfc5549_ebgp_unnumbered_nbr.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 
 # Global variables
 NO_OF_RTES = 2
@@ -124,21 +116,6 @@ shut / no shut of nexthop and BGP peer interfaces
  """
 
 
-class CreateTopo(Topo):
-    """
-    Test topology builder.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """Set up the pytest environment."""
     global topo, ADDR_TYPES
@@ -150,7 +127,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/rfc5549_ebgp_unnumbered_nbr.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
 
     # Starting topology, create tmp files which are loaded to routers
     #  to start deamons and then start routers
diff --git a/tests/topotests/bgp_ipv4_over_ipv6/test_rfc5549_ibgp_nbr.py b/tests/topotests/bgp_ipv4_over_ipv6/test_rfc5549_ibgp_nbr.py
index 871f6b128..9b5e48e08 100644
--- a/tests/topotests/bgp_ipv4_over_ipv6/test_rfc5549_ibgp_nbr.py
+++ b/tests/topotests/bgp_ipv4_over_ipv6/test_rfc5549_ibgp_nbr.py
@@ -39,7 +39,6 @@ sys.path.append(os.path.join(CWD, "../../"))
 # pylint: disable=C0413
 # Import topogen and topotest helpers
 from lib.topogen import Topogen, get_topogen
-from mininet.topo import Topo
 
 from lib.common_config import (
     start_topology,
@@ -67,13 +66,6 @@ from lib.topojson import build_topo_from_json, build_config_from_json
 
 # Global variables
 topo = None
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/rfc5549_ibgp_nbr.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 
 # Global variables
 NETWORK = {
@@ -121,21 +113,6 @@ TESTCASES = """
  """
 
 
-class CreateTopo(Topo):
-    """
-    Test topology builder.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """Set up the pytest environment."""
 
@@ -147,7 +124,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/rfc5549_ibgp_nbr.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
 
     # Starting topology, create tmp files which are loaded to routers
     #  to start deamons and then start routers
diff --git a/tests/topotests/bgp_ipv4_over_ipv6/test_rfc5549_ibgp_unnumbered_nbr.py b/tests/topotests/bgp_ipv4_over_ipv6/test_rfc5549_ibgp_unnumbered_nbr.py
index 5f4292b81..5e804df23 100644
--- a/tests/topotests/bgp_ipv4_over_ipv6/test_rfc5549_ibgp_unnumbered_nbr.py
+++ b/tests/topotests/bgp_ipv4_over_ipv6/test_rfc5549_ibgp_unnumbered_nbr.py
@@ -38,7 +38,6 @@ sys.path.append(os.path.join(CWD, "../../"))
 # pylint: disable=C0413
 # Import topogen and topotest helpers
 from lib.topogen import Topogen, get_topogen
-from mininet.topo import Topo
 
 from lib.common_config import (
     start_topology,
@@ -58,13 +57,6 @@ from lib.topojson import build_topo_from_json, build_config_from_json
 
 # Global variables
 topo = None
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/rfc5549_ibgp_unnumbered_nbr.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 
 
 # Global variables
@@ -107,21 +99,6 @@ TESTCASES = """
  """
 
 
-class CreateTopo(Topo):
-    """
-    Test topology builder.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """Set up the pytest environment."""
 
@@ -133,7 +110,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/rfc5549_ibgp_unnumbered_nbr.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
 
     # Starting topology, create tmp files which are loaded to routers
     #  to start deamons and then start routers
diff --git a/tests/topotests/bgp_ipv6_rtadv/test_bgp_ipv6_rtadv.py b/tests/topotests/bgp_ipv6_rtadv/test_bgp_ipv6_rtadv.py
index dc587cd70..04cf0395d 100644
--- a/tests/topotests/bgp_ipv6_rtadv/test_bgp_ipv6_rtadv.py
+++ b/tests/topotests/bgp_ipv6_rtadv/test_bgp_ipv6_rtadv.py
@@ -49,25 +49,21 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class BGPIPV6RTADVTopo(Topo):
-    "Test topology builder"
+def build_topo(tgen):
+    "Build function"
 
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+    # Create 2 routers.
+    tgen.add_router("r1")
+    tgen.add_router("r2")
 
-        # Create 2 routers.
-        tgen.add_router("r1")
-        tgen.add_router("r2")
-
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(BGPIPV6RTADVTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_l3vpn_to_bgp_direct/customize.py b/tests/topotests/bgp_l3vpn_to_bgp_direct/customize.py
index 6eaf8e07f..f344ee76b 100644
--- a/tests/topotests/bgp_l3vpn_to_bgp_direct/customize.py
+++ b/tests/topotests/bgp_l3vpn_to_bgp_direct/customize.py
@@ -94,48 +94,44 @@ CWD = os.path.dirname(os.path.realpath(__file__))
 TEST = os.path.basename(CWD)
 
 
-class ThisTestTopo(Topo):
-    "Test topology builder"
-
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
-
-        # This function only purpose is to define allocation and relationship
-        # between routers, switches and hosts.
-        #
-        # Create P/PE routers
-        tgen.add_router("r1")
-        # check for mpls
-        if tgen.hasmpls != True:
-            logger.info("MPLS not available, tests will be skipped")
-            return
-        for routern in range(2, 5):
-            tgen.add_router("r{}".format(routern))
-        # Create CE routers
-        for routern in range(1, 4):
-            tgen.add_router("ce{}".format(routern))
-
-        # CE/PE links
-        tgen.add_link(tgen.gears["ce1"], tgen.gears["r1"], "ce1-eth0", "r1-eth4")
-        tgen.add_link(tgen.gears["ce2"], tgen.gears["r3"], "ce2-eth0", "r3-eth4")
-        tgen.add_link(tgen.gears["ce3"], tgen.gears["r4"], "ce3-eth0", "r4-eth4")
-
-        # Create a switch with just one router connected to it to simulate a
-        # empty network.
-        switch = {}
-        switch[0] = tgen.add_switch("sw0")
-        switch[0].add_link(tgen.gears["r1"], nodeif="r1-eth0")
-        switch[0].add_link(tgen.gears["r2"], nodeif="r2-eth0")
-
-        switch[1] = tgen.add_switch("sw1")
-        switch[1].add_link(tgen.gears["r2"], nodeif="r2-eth1")
-        switch[1].add_link(tgen.gears["r3"], nodeif="r3-eth0")
-        switch[1].add_link(tgen.gears["r4"], nodeif="r4-eth0")
-
-        switch[1] = tgen.add_switch("sw2")
-        switch[1].add_link(tgen.gears["r2"], nodeif="r2-eth2")
-        switch[1].add_link(tgen.gears["r3"], nodeif="r3-eth1")
+def build_topo(tgen):
+    "Build function"
+
+    # This function only purpose is to define allocation and relationship
+    # between routers, switches and hosts.
+    #
+    # Create P/PE routers
+    tgen.add_router("r1")
+    # check for mpls
+    if tgen.hasmpls != True:
+        logger.info("MPLS not available, tests will be skipped")
+        return
+    for routern in range(2, 5):
+        tgen.add_router("r{}".format(routern))
+    # Create CE routers
+    for routern in range(1, 4):
+        tgen.add_router("ce{}".format(routern))
+
+    # CE/PE links
+    tgen.add_link(tgen.gears["ce1"], tgen.gears["r1"], "ce1-eth0", "r1-eth4")
+    tgen.add_link(tgen.gears["ce2"], tgen.gears["r3"], "ce2-eth0", "r3-eth4")
+    tgen.add_link(tgen.gears["ce3"], tgen.gears["r4"], "ce3-eth0", "r4-eth4")
+
+    # Create a switch with just one router connected to it to simulate a
+    # empty network.
+    switch = {}
+    switch[0] = tgen.add_switch("sw0")
+    switch[0].add_link(tgen.gears["r1"], nodeif="r1-eth0")
+    switch[0].add_link(tgen.gears["r2"], nodeif="r2-eth0")
+
+    switch[1] = tgen.add_switch("sw1")
+    switch[1].add_link(tgen.gears["r2"], nodeif="r2-eth1")
+    switch[1].add_link(tgen.gears["r3"], nodeif="r3-eth0")
+    switch[1].add_link(tgen.gears["r4"], nodeif="r4-eth0")
+
+    switch[1] = tgen.add_switch("sw2")
+    switch[1].add_link(tgen.gears["r2"], nodeif="r2-eth2")
+    switch[1].add_link(tgen.gears["r3"], nodeif="r3-eth1")
 
 
 def ltemplatePreRouterStartHook():
diff --git a/tests/topotests/bgp_l3vpn_to_bgp_vrf/customize.py b/tests/topotests/bgp_l3vpn_to_bgp_vrf/customize.py
index 40009b9ba..91291d89e 100644
--- a/tests/topotests/bgp_l3vpn_to_bgp_vrf/customize.py
+++ b/tests/topotests/bgp_l3vpn_to_bgp_vrf/customize.py
@@ -95,54 +95,50 @@ CWD = os.path.dirname(os.path.realpath(__file__))
 TEST = os.path.basename(CWD)
 
 
-class ThisTestTopo(Topo):
-    "Test topology builder"
-
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
-
-        # This function only purpose is to define allocation and relationship
-        # between routers, switches and hosts.
-        #
-        # Create P/PE routers
-        # check for mpls
-        tgen.add_router("r1")
-        if tgen.hasmpls != True:
-            logger.info("MPLS not available, tests will be skipped")
-            return
-        mach = platform.machine()
-        krel = platform.release()
-        if mach[:1] == "a" and topotest.version_cmp(krel, "4.11") < 0:
-            logger.info("Need Kernel version 4.11 to run on arm processor")
-            return
-        for routern in range(2, 5):
-            tgen.add_router("r{}".format(routern))
-        # Create CE routers
-        for routern in range(1, 5):
-            tgen.add_router("ce{}".format(routern))
-
-        # CE/PE links
-        tgen.add_link(tgen.gears["ce1"], tgen.gears["r1"], "ce1-eth0", "r1-eth4")
-        tgen.add_link(tgen.gears["ce2"], tgen.gears["r3"], "ce2-eth0", "r3-eth4")
-        tgen.add_link(tgen.gears["ce3"], tgen.gears["r4"], "ce3-eth0", "r4-eth4")
-        tgen.add_link(tgen.gears["ce4"], tgen.gears["r4"], "ce4-eth0", "r4-eth5")
-
-        # Create a switch with just one router connected to it to simulate a
-        # empty network.
-        switch = {}
-        switch[0] = tgen.add_switch("sw0")
-        switch[0].add_link(tgen.gears["r1"], nodeif="r1-eth0")
-        switch[0].add_link(tgen.gears["r2"], nodeif="r2-eth0")
-
-        switch[1] = tgen.add_switch("sw1")
-        switch[1].add_link(tgen.gears["r2"], nodeif="r2-eth1")
-        switch[1].add_link(tgen.gears["r3"], nodeif="r3-eth0")
-        switch[1].add_link(tgen.gears["r4"], nodeif="r4-eth0")
-
-        switch[1] = tgen.add_switch("sw2")
-        switch[1].add_link(tgen.gears["r2"], nodeif="r2-eth2")
-        switch[1].add_link(tgen.gears["r3"], nodeif="r3-eth1")
+def build_topo(tgen):
+    "Build function"
+
+    # This function only purpose is to define allocation and relationship
+    # between routers, switches and hosts.
+    #
+    # Create P/PE routers
+    # check for mpls
+    tgen.add_router("r1")
+    if tgen.hasmpls != True:
+        logger.info("MPLS not available, tests will be skipped")
+        return
+    mach = platform.machine()
+    krel = platform.release()
+    if mach[:1] == "a" and topotest.version_cmp(krel, "4.11") < 0:
+        logger.info("Need Kernel version 4.11 to run on arm processor")
+        return
+    for routern in range(2, 5):
+        tgen.add_router("r{}".format(routern))
+    # Create CE routers
+    for routern in range(1, 5):
+        tgen.add_router("ce{}".format(routern))
+
+    # CE/PE links
+    tgen.add_link(tgen.gears["ce1"], tgen.gears["r1"], "ce1-eth0", "r1-eth4")
+    tgen.add_link(tgen.gears["ce2"], tgen.gears["r3"], "ce2-eth0", "r3-eth4")
+    tgen.add_link(tgen.gears["ce3"], tgen.gears["r4"], "ce3-eth0", "r4-eth4")
+    tgen.add_link(tgen.gears["ce4"], tgen.gears["r4"], "ce4-eth0", "r4-eth5")
+
+    # Create a switch with just one router connected to it to simulate a
+    # empty network.
+    switch = {}
+    switch[0] = tgen.add_switch("sw0")
+    switch[0].add_link(tgen.gears["r1"], nodeif="r1-eth0")
+    switch[0].add_link(tgen.gears["r2"], nodeif="r2-eth0")
+
+    switch[1] = tgen.add_switch("sw1")
+    switch[1].add_link(tgen.gears["r2"], nodeif="r2-eth1")
+    switch[1].add_link(tgen.gears["r3"], nodeif="r3-eth0")
+    switch[1].add_link(tgen.gears["r4"], nodeif="r4-eth0")
+
+    switch[1] = tgen.add_switch("sw2")
+    switch[1].add_link(tgen.gears["r2"], nodeif="r2-eth2")
+    switch[1].add_link(tgen.gears["r3"], nodeif="r3-eth1")
 
 
 def ltemplatePreRouterStartHook():
diff --git a/tests/topotests/bgp_large_community/test_bgp_large_community_topo_1.py b/tests/topotests/bgp_large_community/test_bgp_large_community_topo_1.py
index d138a689e..fb472c449 100644
--- a/tests/topotests/bgp_large_community/test_bgp_large_community_topo_1.py
+++ b/tests/topotests/bgp_large_community/test_bgp_large_community_topo_1.py
@@ -81,13 +81,6 @@ CWD = os_path.dirname(os_path.realpath(__file__))
 sys.path.append(os_path.join(CWD, "../"))
 sys.path.append(os_path.join(CWD, "../lib/"))
 
-# Reading the data from JSON File for topology and configuration creation
-jsonFile = "{}/bgp_large_community_topo_1.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json_load(topoJson)
-except IOError:
-    logger.info("Could not read file:", jsonFile)
 
 # Global variables
 bgp_convergence = False
@@ -124,22 +117,6 @@ STANDARD_COMM = {
 }
 
 
-class CreateTopo(Topo):
-    """
-    Test topology builder
-
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function"""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
@@ -159,7 +136,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/bgp_large_community_topo_1.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/bgp_large_community/test_bgp_large_community_topo_2.py b/tests/topotests/bgp_large_community/test_bgp_large_community_topo_2.py
index c9115bf42..a94d20da3 100644
--- a/tests/topotests/bgp_large_community/test_bgp_large_community_topo_2.py
+++ b/tests/topotests/bgp_large_community/test_bgp_large_community_topo_2.py
@@ -97,17 +97,9 @@ from lib.topolog import logger
 from lib.bgp import verify_bgp_convergence, create_router_bgp, clear_bgp_and_verify
 from lib.topojson import build_topo_from_json, build_config_from_json
 
-pytestmark = [pytest.mark.bgpd]
-
 
-# Reading the data from JSON File for topology and configuration creation
-jsonFile = "{}/bgp_large_community_topo_2.json".format(CWD)
+pytestmark = [pytest.mark.bgpd]
 
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 
 # Global variables
 bgp_convergence = False
@@ -115,21 +107,6 @@ bgp_convergence = False
 NETWORKS = {"ipv4": ["200.50.2.0/32"], "ipv6": ["1::1/128"]}
 
 
-class GenerateTopo(Topo):
-    """
-    Test topology builder
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
@@ -149,7 +126,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(GenerateTopo, mod.__name__)
+    json_file = "{}/bgp_large_community_topo_2.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/bgp_link_bw_ip/test_bgp_linkbw_ip.py b/tests/topotests/bgp_link_bw_ip/test_bgp_linkbw_ip.py
index 4ad1dbcaa..799b5f93f 100644
--- a/tests/topotests/bgp_link_bw_ip/test_bgp_linkbw_ip.py
+++ b/tests/topotests/bgp_link_bw_ip/test_bgp_linkbw_ip.py
@@ -66,62 +66,57 @@ this scenario, the servers are also routers as they have to announce
 anycast IP (VIP) addresses via BGP.
 """
 
-
-class BgpLinkBwTopo(Topo):
-    "Test topology builder"
-
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
-
-        # Create 10 routers - 1 super-spine, 2 spines, 3 leafs
-        # and 4 servers
-        routers = {}
-        for i in range(1, 11):
-            routers[i] = tgen.add_router("r{}".format(i))
-
-        # Create 13 "switches" - to interconnect the above routers
-        switches = {}
-        for i in range(1, 14):
-            switches[i] = tgen.add_switch("s{}".format(i))
-
-        # Interconnect R1 (super-spine) to R2 and R3 (the two spines)
-        switches[1].add_link(tgen.gears["r1"])
-        switches[1].add_link(tgen.gears["r2"])
-        switches[2].add_link(tgen.gears["r1"])
-        switches[2].add_link(tgen.gears["r3"])
-
-        # Interconnect R2 (spine in pod-1) to R4 and R5 (the associated
-        # leaf switches)
-        switches[3].add_link(tgen.gears["r2"])
-        switches[3].add_link(tgen.gears["r4"])
-        switches[4].add_link(tgen.gears["r2"])
-        switches[4].add_link(tgen.gears["r5"])
-
-        # Interconnect R3 (spine in pod-2) to R6 (associated leaf)
-        switches[5].add_link(tgen.gears["r3"])
-        switches[5].add_link(tgen.gears["r6"])
-
-        # Interconnect leaf switches to servers
-        switches[6].add_link(tgen.gears["r4"])
-        switches[6].add_link(tgen.gears["r7"])
-        switches[7].add_link(tgen.gears["r4"])
-        switches[7].add_link(tgen.gears["r8"])
-        switches[8].add_link(tgen.gears["r5"])
-        switches[8].add_link(tgen.gears["r9"])
-        switches[9].add_link(tgen.gears["r6"])
-        switches[9].add_link(tgen.gears["r10"])
-
-        # Create empty networks for the servers
-        switches[10].add_link(tgen.gears["r7"])
-        switches[11].add_link(tgen.gears["r8"])
-        switches[12].add_link(tgen.gears["r9"])
-        switches[13].add_link(tgen.gears["r10"])
+def build_topo(tgen):
+    "Build function"
+
+    # Create 10 routers - 1 super-spine, 2 spines, 3 leafs
+    # and 4 servers
+    routers = {}
+    for i in range(1, 11):
+        routers[i] = tgen.add_router("r{}".format(i))
+
+    # Create 13 "switches" - to interconnect the above routers
+    switches = {}
+    for i in range(1, 14):
+        switches[i] = tgen.add_switch("s{}".format(i))
+
+    # Interconnect R1 (super-spine) to R2 and R3 (the two spines)
+    switches[1].add_link(tgen.gears["r1"])
+    switches[1].add_link(tgen.gears["r2"])
+    switches[2].add_link(tgen.gears["r1"])
+    switches[2].add_link(tgen.gears["r3"])
+
+    # Interconnect R2 (spine in pod-1) to R4 and R5 (the associated
+    # leaf switches)
+    switches[3].add_link(tgen.gears["r2"])
+    switches[3].add_link(tgen.gears["r4"])
+    switches[4].add_link(tgen.gears["r2"])
+    switches[4].add_link(tgen.gears["r5"])
+
+    # Interconnect R3 (spine in pod-2) to R6 (associated leaf)
+    switches[5].add_link(tgen.gears["r3"])
+    switches[5].add_link(tgen.gears["r6"])
+
+    # Interconnect leaf switches to servers
+    switches[6].add_link(tgen.gears["r4"])
+    switches[6].add_link(tgen.gears["r7"])
+    switches[7].add_link(tgen.gears["r4"])
+    switches[7].add_link(tgen.gears["r8"])
+    switches[8].add_link(tgen.gears["r5"])
+    switches[8].add_link(tgen.gears["r9"])
+    switches[9].add_link(tgen.gears["r6"])
+    switches[9].add_link(tgen.gears["r10"])
+
+    # Create empty networks for the servers
+    switches[10].add_link(tgen.gears["r7"])
+    switches[11].add_link(tgen.gears["r8"])
+    switches[12].add_link(tgen.gears["r9"])
+    switches[13].add_link(tgen.gears["r10"])
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(BgpLinkBwTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_listen_on_multiple_addresses/test_bgp_listen_on_multiple_addresses.py b/tests/topotests/bgp_listen_on_multiple_addresses/test_bgp_listen_on_multiple_addresses.py
index fdbc5e553..bc4336b6f 100755
--- a/tests/topotests/bgp_listen_on_multiple_addresses/test_bgp_listen_on_multiple_addresses.py
+++ b/tests/topotests/bgp_listen_on_multiple_addresses/test_bgp_listen_on_multiple_addresses.py
@@ -67,27 +67,12 @@ LISTEN_ADDRESSES = {
 }
 
 
-# Reads data from JSON File for topology and configuration creation.
-jsonFile = "{}/bgp_listen_on_multiple_addresses.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
-
-
-class TemplateTopo(Topo):
-    "Topology builder."
-
-    def build(self, *_args, **_opts):
-        "Defines the allocation and relationship between routers and switches."
-        tgen = get_topogen(self)
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     "Sets up the test environment."
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    json_file = "{}/bgp_listen_on_multiple_addresses.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
 
     # Adds extra parameters to bgpd so they listen for connections on specific
     # multiple addresses.
diff --git a/tests/topotests/bgp_local_as_private_remove/test_bgp_local_as_private_remove.py b/tests/topotests/bgp_local_as_private_remove/test_bgp_local_as_private_remove.py
index ec4919650..f648e1791 100644
--- a/tests/topotests/bgp_local_as_private_remove/test_bgp_local_as_private_remove.py
+++ b/tests/topotests/bgp_local_as_private_remove/test_bgp_local_as_private_remove.py
@@ -46,24 +46,21 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    for routern in range(1, 5):
+        tgen.add_router("r{}".format(routern))
 
-        for routern in range(1, 5):
-            tgen.add_router("r{}".format(routern))
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
-
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["r3"])
-        switch.add_link(tgen.gears["r4"])
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r3"])
+    switch.add_link(tgen.gears["r4"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_lu_topo1/test_bgp_lu.py b/tests/topotests/bgp_lu_topo1/test_bgp_lu.py
index 258ddb148..6318044ea 100644
--- a/tests/topotests/bgp_lu_topo1/test_bgp_lu.py
+++ b/tests/topotests/bgp_lu_topo1/test_bgp_lu.py
@@ -62,37 +62,33 @@ pytestmark = [pytest.mark.bgpd]
 # +-----+                +-----+                 +-----+
 
 
-class TemplateTopo(Topo):
-    "Test topology builder"
+def build_topo(tgen):
+    "Build function"
 
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+    # This function only purpose is to define allocation and relationship
+    # between routers, switches and hosts.
+    #
+    #
+    # Create routers
+    tgen.add_router("R1")
+    tgen.add_router("R2")
+    tgen.add_router("R3")
 
-        # This function only purpose is to define allocation and relationship
-        # between routers, switches and hosts.
-        #
-        #
-        # Create routers
-        tgen.add_router("R1")
-        tgen.add_router("R2")
-        tgen.add_router("R3")
+    # R1-R2
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["R1"])
+    switch.add_link(tgen.gears["R2"])
 
-        # R1-R2
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["R1"])
-        switch.add_link(tgen.gears["R2"])
-
-        # R2-R3
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["R2"])
-        switch.add_link(tgen.gears["R3"])
+    # R2-R3
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["R2"])
+    switch.add_link(tgen.gears["R3"])
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     # ... and here it calls Mininet initialization functions.
     tgen.start_topology()
 
diff --git a/tests/topotests/bgp_maximum_prefix_invalid_update/test_bgp_maximum_prefix_invalid_update.py b/tests/topotests/bgp_maximum_prefix_invalid_update/test_bgp_maximum_prefix_invalid_update.py
index c80094684..66fcd355e 100644
--- a/tests/topotests/bgp_maximum_prefix_invalid_update/test_bgp_maximum_prefix_invalid_update.py
+++ b/tests/topotests/bgp_maximum_prefix_invalid_update/test_bgp_maximum_prefix_invalid_update.py
@@ -50,20 +50,17 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    for routern in range(1, 3):
+        tgen.add_router("r{}".format(routern))
 
-        for routern in range(1, 3):
-            tgen.add_router("r{}".format(routern))
-
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_maximum_prefix_out/test_bgp_maximum_prefix_out.py b/tests/topotests/bgp_maximum_prefix_out/test_bgp_maximum_prefix_out.py
index 5b762bfe5..07d1cb02b 100644
--- a/tests/topotests/bgp_maximum_prefix_out/test_bgp_maximum_prefix_out.py
+++ b/tests/topotests/bgp_maximum_prefix_out/test_bgp_maximum_prefix_out.py
@@ -46,20 +46,17 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    for routern in range(1, 3):
+        tgen.add_router("r{}".format(routern))
 
-        for routern in range(1, 3):
-            tgen.add_router("r{}".format(routern))
-
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_minimum_holdtime/test_bgp_minimum_holdtime.py b/tests/topotests/bgp_minimum_holdtime/test_bgp_minimum_holdtime.py
index c5afcdf11..5facdd26e 100755
--- a/tests/topotests/bgp_minimum_holdtime/test_bgp_minimum_holdtime.py
+++ b/tests/topotests/bgp_minimum_holdtime/test_bgp_minimum_holdtime.py
@@ -41,20 +41,17 @@ from mininet.topo import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    for routern in range(1, 3):
+        tgen.add_router("r{}".format(routern))
 
-        for routern in range(1, 3):
-            tgen.add_router("r{}".format(routern))
-
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_multi_vrf_topo1/test_bgp_multi_vrf_topo1.py b/tests/topotests/bgp_multi_vrf_topo1/test_bgp_multi_vrf_topo1.py
index 9a20f7d45..ffa1c3fb6 100644
--- a/tests/topotests/bgp_multi_vrf_topo1/test_bgp_multi_vrf_topo1.py
+++ b/tests/topotests/bgp_multi_vrf_topo1/test_bgp_multi_vrf_topo1.py
@@ -145,15 +145,9 @@ from lib.bgp import (
 )
 from lib.topojson import build_topo_from_json, build_config_from_json
 
+
 pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/bgp_multi_vrf_topo1.json".format(CWD)
 
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 
 # Global variables
 NETWORK1_1 = {"ipv4": "1.1.1.1/32", "ipv6": "1::1/128"}
@@ -185,21 +179,6 @@ LOOPBACK_2 = {
 }
 
 
-class CreateTopo(Topo):
-    """
-    Test BasicTopo - topology 1
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function"""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
@@ -222,7 +201,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/bgp_multi_vrf_topo1.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/bgp_multi_vrf_topo2/test_bgp_multi_vrf_topo2.py b/tests/topotests/bgp_multi_vrf_topo2/test_bgp_multi_vrf_topo2.py
index 7fd9fac6e..609fdf358 100644
--- a/tests/topotests/bgp_multi_vrf_topo2/test_bgp_multi_vrf_topo2.py
+++ b/tests/topotests/bgp_multi_vrf_topo2/test_bgp_multi_vrf_topo2.py
@@ -105,14 +105,6 @@ from lib.topojson import build_config_from_json, build_topo_from_json
 pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
 
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/bgp_multi_vrf_topo2.json".format(CWD)
-
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 
 # Global variables
 NETWORK1_1 = {"ipv4": "1.1.1.1/32", "ipv6": "1::1/128"}
@@ -139,21 +131,6 @@ HOLDDOWNTIMER = 3
 PREFERRED_NEXT_HOP = "link_local"
 
 
-class CreateTopo(Topo):
-    """
-    Test BasicTopo - topology 1
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function"""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
@@ -176,7 +153,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/bgp_multi_vrf_topo2.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/bgp_multiview_topo1/test_bgp_multiview_topo1.py b/tests/topotests/bgp_multiview_topo1/test_bgp_multiview_topo1.py
index a949c5282..25240791c 100644
--- a/tests/topotests/bgp_multiview_topo1/test_bgp_multiview_topo1.py
+++ b/tests/topotests/bgp_multiview_topo1/test_bgp_multiview_topo1.py
@@ -74,8 +74,7 @@ from functools import partial
 
 sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 from lib import topotest
-from lib.micronet_compat import Mininet
-from lib.micronet_compat import Topo
+from lib.topogen import get_topogen, Topogen
 
 
 pytestmark = [pytest.mark.bgpd]
@@ -91,38 +90,28 @@ fatal_error = ""
 #####################################################
 
 
-class NetworkTopo(Topo):
-    "BGP Multiview Topology 1"
+def build_topo(tgen):
+    # Setup Routers
+    router = tgen.add_router("r1")
 
-    def build(self, **_opts):
+    # Setup Provider BGP peers
+    peer = {}
+    for i in range(1, 9):
+        peer[i] = tgen.add_exabgp_peer(
+            "peer%s" % i,
+            ip="172.16.1.%s/24" % i,
+            defaultRoute="via 172.16.1.254"
+        )
 
-        exabgpPrivateDirs = ["/etc/exabgp", "/var/run/exabgp", "/var/log"]
+    # First switch is for a dummy interface (for local network)
+    switch = tgen.add_switch("sw0")
+    switch.add_link(router, nodeif="r1-stub")
 
-        # Setup Routers
-        router = {}
-        for i in range(1, 2):
-            router[i] = topotest.addRouter(self, "r%s" % i)
-
-        # Setup Provider BGP peers
-        peer = {}
-        for i in range(1, 9):
-            peer[i] = self.addHost(
-                "peer%s" % i,
-                ip="172.16.1.%s/24" % i,
-                defaultRoute="via 172.16.1.254",
-                privateDirs=exabgpPrivateDirs,
-            )
-
-        # Setup Switches
-        switch = {}
-        # First switch is for a dummy interface (for local network)
-        switch[0] = self.addSwitch("sw0")
-        self.addLink(switch[0], router[1], intfName2="r1-stub")
-        # Second switch is for connection to all peering routers
-        switch[1] = self.addSwitch("sw1")
-        self.addLink(switch[1], router[1], intfName2="r1-eth0")
-        for j in range(1, 9):
-            self.addLink(switch[1], peer[j], intfName2="peer%s-eth0" % j)
+    # Second switch is for connection to all peering routers
+    switch = tgen.add_switch("sw1")
+    switch.add_link(router, nodeif="r1-eth0")
+    for j in range(1, 9):
+        switch.add_link(peer[j], nodeif="peer%s-eth0" % j)
 
 
 #####################################################
@@ -133,87 +122,43 @@ class NetworkTopo(Topo):
 
 
 def setup_module(module):
-    global topo, net
-
-    print("\n\n** %s: Setup Topology" % module.__name__)
-    print("******************************************\n")
-
-    print("Cleanup old Mininet runs")
-    os.system("sudo mn -c > /dev/null 2>&1")
-
     thisDir = os.path.dirname(os.path.realpath(__file__))
-    topo = NetworkTopo()
-
-    net = Mininet(controller=None, topo=topo)
-    net.start()
+    tgen = Topogen(build_topo, module.__name__)
+    tgen.start_topology()
 
     # Starting Routers
-    for i in range(1, 2):
-        net["r%s" % i].loadConf("zebra", "%s/r%s/zebra.conf" % (thisDir, i))
-        net["r%s" % i].loadConf("bgpd", "%s/r%s/bgpd.conf" % (thisDir, i))
-        net["r%s" % i].startRouter()
+    router = tgen.net["r1"]
+    router.loadConf("zebra", "%s/r1/zebra.conf" % thisDir)
+    router.loadConf("bgpd", "%s/r1/bgpd.conf" % thisDir)
+    tgen.gears["r1"].start()
 
     # Starting PE Hosts and init ExaBGP on each of them
-    print("*** Starting BGP on all 8 Peers")
-    for i in range(1, 9):
-        net["peer%s" % i].cmd("cp %s/exabgp.env /etc/exabgp/exabgp.env" % thisDir)
-        net["peer%s" % i].cmd("cp %s/peer%s/* /etc/exabgp/" % (thisDir, i))
-        net["peer%s" % i].cmd("chmod 644 /etc/exabgp/*")
-        net["peer%s" % i].cmd("chmod 755 /etc/exabgp/*.py")
-        net["peer%s" % i].cmd("chown -R exabgp:exabgp /etc/exabgp")
-        net["peer%s" % i].cmd("exabgp -e /etc/exabgp/exabgp.env /etc/exabgp/exabgp.cfg")
-        print("peer%s" % i),
-    print("")
-
-    # For debugging after starting FRR daemons, uncomment the next line
-    # CLI(net)
+    peer_list = tgen.exabgp_peers()
+    for pname, peer in peer_list.items():
+        peer_dir = os.path.join(thisDir, pname)
+        env_file = os.path.join(thisDir, "exabgp.env")
+        peer.start(peer_dir, env_file)
 
 
 def teardown_module(module):
-    global net
-
-    print("\n\n** %s: Shutdown Topology" % module.__name__)
-    print("******************************************\n")
-
-    # Shutdown - clean up everything
-    print("*** Killing BGP on Peer routers")
-    # Killing ExaBGP
-    for i in range(1, 9):
-        net["peer%s" % i].cmd("kill `cat /var/run/exabgp/exabgp.pid`")
-
-    # End - Shutdown network
-    net.stop()
+    tgen = get_topogen()
+    tgen.stop_topology()
 
 
 def test_router_running():
-    global fatal_error
-    global net
-
-    # Skip if previous fatal error condition is raised
-    if fatal_error != "":
-        pytest.skip(fatal_error)
-
-    print("\n\n** Check if FRR is running on each Router node")
-    print("******************************************\n")
-
-    # Starting Routers
-    for i in range(1, 2):
-        fatal_error = net["r%s" % i].checkRouterRunning()
-        assert fatal_error == "", fatal_error
+    tgen = get_topogen()
 
-    # For debugging after starting FRR daemons, uncomment the next line
-    # CLI(net)
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
 
 
 def test_bgp_converge():
     "Check for BGP converged on all peers and BGP views"
 
-    global fatal_error
-    global net
+    tgen = get_topogen()
 
-    # Skip if previous fatal error condition is raised
-    if fatal_error != "":
-        pytest.skip(fatal_error)
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
 
     # Wait for BGP to converge  (All Neighbors in either Full or TwoWay State)
 
@@ -224,7 +169,7 @@ def test_bgp_converge():
         # Look for any node not yet converged
         for i in range(1, 2):
             for view in range(1, 4):
-                notConverged = net["r%s" % i].cmd(
+                notConverged = tgen.net["r%s" % i].cmd(
                     'vtysh -c "show ip bgp view %s summary" 2> /dev/null | grep ^[0-9] | grep -vP " 11\s+(\d+)"'
                     % view
                 )
@@ -242,7 +187,7 @@ def test_bgp_converge():
             break
     else:
         # Bail out with error if a router fails to converge
-        bgpStatus = net["r%s" % i].cmd('vtysh -c "show ip bgp view %s summary"' % view)
+        bgpStatus = tgen.net["r%s" % i].cmd('vtysh -c "show ip bgp view %s summary"' % view)
         assert False, "BGP did not converge:\n%s" % bgpStatus
 
     # Wait for an extra 5s to announce all routes
@@ -256,53 +201,92 @@ def test_bgp_converge():
     #     print("\nwaiting 15s for routes to populate")
     #     sleep(15)
 
-    # Make sure that all daemons are running
-    for i in range(1, 2):
-        fatal_error = net["r%s" % i].checkRouterRunning()
-        assert fatal_error == "", fatal_error
-
-    # For debugging after starting FRR daemons, uncomment the next line
-    # CLI(net)
+    tgen.routers_have_failure()
 
 
 def test_bgp_routingTable():
-    global fatal_error
-    global net
-    # Skip if previous fatal error condition is raised
-    if fatal_error != "":
-        pytest.skip(fatal_error)
+    tgen = get_topogen()
+
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
+
     thisDir = os.path.dirname(os.path.realpath(__file__))
-    print("Verifying BGP Routing Tables")
-    def router_json_cmp(router, cmd, data):
-        json_data = json.loads(router.cmd("vtysh -c \"{}\" 2> /dev/null".format(cmd)))
-        return topotest.json_cmp(json_data, data)
-    router = net["r1"]
-    for view in range(1, 4):
-        json_file = "{}/{}/view_{}.json".format(thisDir, router.name, view)
-        expected = json.loads(open(json_file).read())
-        test_func = partial(
-            router_json_cmp, router, "show ip bgp view {} json".format(view), expected
-        )
-        _, result = topotest.run_and_expect(test_func, None, count=5, wait=1)
-        assertmsg = "Routing Table verification failed for router {}, view {}".format(
-            router.name, view
-        )
-        assert result is None, assertmsg
-    # Make sure that all daemons are running
+
+    print("\n\n** Verifying BGP Routing Tables")
+    print("******************************************\n")
+    diffresult = {}
     for i in range(1, 2):
-        fatal_error = net["r%s" % i].checkRouterRunning()
-        assert fatal_error == "", fatal_error
-    # For debugging after starting FRR daemons, uncomment the next line
-    # CLI(net)
+        for view in range(1, 4):
+            success = 0
+            # This glob pattern should work as long as number of views < 10
+            for refTableFile in glob.glob(
+                "%s/r%s/show_ip_bgp_view_%s*.ref" % (thisDir, i, view)
+            ):
+
+                if os.path.isfile(refTableFile):
+                    # Read expected result from file
+                    expected = open(refTableFile).read().rstrip()
+                    # Fix newlines (make them all the same)
+                    expected = ("\n".join(expected.splitlines()) + "\n").splitlines(1)
+
+                    # Actual output from router
+                    actual = (
+                        tgen.net["r%s" % i]
+                        .cmd('vtysh -c "show ip bgp view %s" 2> /dev/null' % view)
+                        .rstrip()
+                    )
+
+                    # Fix inconsitent spaces between 0.99.24 and newer versions
+                    actual = re.sub("0             0", "0              0", actual)
+                    actual = re.sub(
+                        r"([0-9])         32768", r"\1          32768", actual
+                    )
+                    # Remove summary line (changed recently)
+                    actual = re.sub(r"Total number.*", "", actual)
+                    actual = re.sub(r"Displayed.*", "", actual)
+                    actual = actual.rstrip()
+                    # Fix table version (ignore it)
+                    actual = re.sub(r"(BGP table version is )[0-9]+", r"\1XXX", actual)
+
+                    # Fix newlines (make them all the same)
+                    actual = ("\n".join(actual.splitlines()) + "\n").splitlines(1)
+
+                # Generate Diff
+                diff = topotest.get_textdiff(
+                    actual,
+                    expected,
+                    title1="actual BGP routing table",
+                    title2="expected BGP routing table",
+                )
+
+                if diff:
+                    diffresult[refTableFile] = diff
+                else:
+                    success = 1
+                    print("template %s matched: r%s ok" % (refTableFile, i))
+                    break
+
+            if not success:
+                resultstr = "No template matched.\n"
+                for f in diffresult.keys():
+                    resultstr += (
+                        "template %s: r%s failed Routing Table Check for view %s:\n%s\n"
+                        % (f, i, view, diffresult[f])
+                    )
+                raise AssertionError(
+                    "Routing Table verification failed for router r%s, view %s:\n%s"
+                    % (i, view, resultstr)
+                )
+
+    tgen.routers_have_failure()
 
 
 def test_shutdown_check_stderr():
-    global fatal_error
-    global net
+    tgen = get_topogen()
 
     # Skip if previous fatal error condition is raised
-    if fatal_error != "":
-        pytest.skip(fatal_error)
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
 
     if os.environ.get("TOPOTESTS_CHECK_STDERR") is None:
         print(
@@ -315,36 +299,22 @@ def test_shutdown_check_stderr():
     print("\n\n** Verifying unexpected STDERR output from daemons")
     print("******************************************\n")
 
-    net["r1"].stopRouter()
+    tgen.net["r1"].stopRouter()
 
-    log = net["r1"].getStdErr("bgpd")
+    log = tgen.net["r1"].getStdErr("bgpd")
     if log:
         print("\nBGPd StdErr Log:\n" + log)
-    log = net["r1"].getStdErr("zebra")
+    log = tgen.net["r1"].getStdErr("zebra")
     if log:
         print("\nZebra StdErr Log:\n" + log)
 
 
 def test_shutdown_check_memleak():
-    global fatal_error
-    global net
-
-    # Skip if previous fatal error condition is raised
-    if fatal_error != "":
-        pytest.skip(fatal_error)
-
-    if os.environ.get("TOPOTESTS_CHECK_MEMLEAK") is None:
-        print(
-            "SKIPPED final check on Memory leaks: Disabled (TOPOTESTS_CHECK_MEMLEAK undefined)\n"
-        )
-        pytest.skip("Skipping test for memory leaks")
-
-    thisDir = os.path.dirname(os.path.realpath(__file__))
+    tgen = get_topogen()
+    if not tgen.is_memleak_enabled():
+        pytest.skip("Memory leak test/report is disabled")
 
-    net["r1"].stopRouter()
-    net["r1"].report_memory_leaks(
-        os.environ.get("TOPOTESTS_CHECK_MEMLEAK"), os.path.basename(__file__)
-    )
+    tgen.report_memory_leaks()
 
 
 if __name__ == "__main__":
diff --git a/tests/topotests/bgp_path_attributes_topo1/test_bgp_path_attributes.py b/tests/topotests/bgp_path_attributes_topo1/test_bgp_path_attributes.py
index 0fc9b7e02..f34ecc30a 100644
--- a/tests/topotests/bgp_path_attributes_topo1/test_bgp_path_attributes.py
+++ b/tests/topotests/bgp_path_attributes_topo1/test_bgp_path_attributes.py
@@ -94,37 +94,14 @@ from lib.bgp import (
 )
 from lib.topojson import build_topo_from_json, build_config_from_json
 
-pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
-
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/bgp_path_attributes.json".format(CWD)
+pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
 
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 
 # Address read from env variables
 ADDR_TYPES = check_address_types()
 
 ####
-class CreateTopo(Topo):
-    """
-    Test CreateTopo - topology 1
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
-
-        # Building topology and configuration from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
@@ -141,7 +118,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/bgp_path_attributes.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/bgp_peer_group/test_bgp_peer-group.py b/tests/topotests/bgp_peer_group/test_bgp_peer-group.py
index 70e49d5cd..172426b2c 100644
--- a/tests/topotests/bgp_peer_group/test_bgp_peer-group.py
+++ b/tests/topotests/bgp_peer_group/test_bgp_peer-group.py
@@ -42,21 +42,18 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    for routern in range(1, 4):
+        tgen.add_router("r{}".format(routern))
 
-        for routern in range(1, 4):
-            tgen.add_router("r{}".format(routern))
-
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_peer_type_multipath_relax/test_bgp_peer-type_multipath-relax.py b/tests/topotests/bgp_peer_type_multipath_relax/test_bgp_peer-type_multipath-relax.py
index c5924c787..4cd14367b 100755
--- a/tests/topotests/bgp_peer_type_multipath_relax/test_bgp_peer-type_multipath-relax.py
+++ b/tests/topotests/bgp_peer_type_multipath_relax/test_bgp_peer-type_multipath-relax.py
@@ -76,32 +76,30 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
 
 
-class PeerTypeRelaxTopo(Topo):
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
-
-        # Set up routers
-        tgen.add_router("r1")  # DUT
-        tgen.add_router("r2")
-
-        # Set up peers
-        for peern in range(1, 5):
-            peer = tgen.add_exabgp_peer(
-                "peer{}".format(peern),
-                ip="10.0.{}.2/24".format(peern),
-                defaultRoute="via 10.0.{}.1".format(peern),
-            )
-            if peern == 2:
-                tgen.add_link(tgen.gears["r2"], peer)
-            else:
-                tgen.add_link(tgen.gears["r1"], peer)
-        tgen.add_link(tgen.gears["r1"], tgen.gears["r2"])
+def build_topo(tgen):
+    "Build function"
+
+    # Set up routers
+    tgen.add_router("r1")  # DUT
+    tgen.add_router("r2")
+
+    # Set up peers
+    for peern in range(1, 5):
+        peer = tgen.add_exabgp_peer(
+            "peer{}".format(peern),
+            ip="10.0.{}.2/24".format(peern),
+            defaultRoute="via 10.0.{}.1".format(peern),
+        )
+        if peern == 2:
+            tgen.add_link(tgen.gears["r2"], peer)
+        else:
+            tgen.add_link(tgen.gears["r1"], peer)
+    tgen.add_link(tgen.gears["r1"], tgen.gears["r2"])
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(PeerTypeRelaxTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     # For all registered routers, load the zebra configuration file
diff --git a/tests/topotests/bgp_prefix_list_topo1/test_prefix_lists.py b/tests/topotests/bgp_prefix_list_topo1/test_prefix_lists.py
index 287ff87bf..f046f442e 100644
--- a/tests/topotests/bgp_prefix_list_topo1/test_prefix_lists.py
+++ b/tests/topotests/bgp_prefix_list_topo1/test_prefix_lists.py
@@ -73,37 +73,14 @@ from lib.topolog import logger
 from lib.bgp import verify_bgp_convergence, create_router_bgp, clear_bgp_and_verify
 from lib.topojson import build_topo_from_json, build_config_from_json
 
-pytestmark = [pytest.mark.bgpd]
-
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/prefix_lists.json".format(CWD)
+pytestmark = [pytest.mark.bgpd]
 
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 
 # Global variables
 bgp_convergence = False
 
 
-class BGPPrefixListTopo(Topo):
-    """
-    Test BGPPrefixListTopo - topology 1
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
@@ -118,7 +95,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(BGPPrefixListTopo, mod.__name__)
+    json_file = "{}/prefix_lists.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/bgp_prefix_sid/test_bgp_prefix_sid.py b/tests/topotests/bgp_prefix_sid/test_bgp_prefix_sid.py
index 72df2eab6..8acf7feae 100644
--- a/tests/topotests/bgp_prefix_sid/test_bgp_prefix_sid.py
+++ b/tests/topotests/bgp_prefix_sid/test_bgp_prefix_sid.py
@@ -44,26 +44,24 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, **_opts):
-        tgen = get_topogen(self)
-        router = tgen.add_router("r1")
-        switch = tgen.add_switch("s1")
-        switch.add_link(router)
-
-        switch = tgen.gears["s1"]
-        peer1 = tgen.add_exabgp_peer(
-            "peer1", ip="10.0.0.101", defaultRoute="via 10.0.0.1"
-        )
-        peer2 = tgen.add_exabgp_peer(
-            "peer2", ip="10.0.0.102", defaultRoute="via 10.0.0.1"
-        )
-        switch.add_link(peer1)
-        switch.add_link(peer2)
+def build_topo(tgen):
+    router = tgen.add_router("r1")
+    switch = tgen.add_switch("s1")
+    switch.add_link(router)
+
+    switch = tgen.gears["s1"]
+    peer1 = tgen.add_exabgp_peer(
+        "peer1", ip="10.0.0.101", defaultRoute="via 10.0.0.1"
+    )
+    peer2 = tgen.add_exabgp_peer(
+        "peer2", ip="10.0.0.102", defaultRoute="via 10.0.0.1"
+    )
+    switch.add_link(peer1)
+    switch.add_link(peer2)
 
 
 def setup_module(module):
-    tgen = Topogen(TemplateTopo, module.__name__)
+    tgen = Topogen(build_topo, module.__name__)
     tgen.start_topology()
 
     router = tgen.gears["r1"]
diff --git a/tests/topotests/bgp_prefix_sid2/test_bgp_prefix_sid2.py b/tests/topotests/bgp_prefix_sid2/test_bgp_prefix_sid2.py
index 6da44faf5..5c85895ed 100755
--- a/tests/topotests/bgp_prefix_sid2/test_bgp_prefix_sid2.py
+++ b/tests/topotests/bgp_prefix_sid2/test_bgp_prefix_sid2.py
@@ -44,22 +44,20 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, **_opts):
-        tgen = get_topogen(self)
-        router = tgen.add_router("r1")
-        switch = tgen.add_switch("s1")
-        switch.add_link(router)
-
-        switch = tgen.gears["s1"]
-        peer1 = tgen.add_exabgp_peer(
-            "peer1", ip="10.0.0.101", defaultRoute="via 10.0.0.1"
-        )
-        switch.add_link(peer1)
+def build_topo(tgen):
+    router = tgen.add_router("r1")
+    switch = tgen.add_switch("s1")
+    switch.add_link(router)
+
+    switch = tgen.gears["s1"]
+    peer1 = tgen.add_exabgp_peer(
+        "peer1", ip="10.0.0.101", defaultRoute="via 10.0.0.1"
+    )
+    switch.add_link(peer1)
 
 
 def setup_module(module):
-    tgen = Topogen(TemplateTopo, module.__name__)
+    tgen = Topogen(build_topo, module.__name__)
     tgen.start_topology()
 
     router = tgen.gears["r1"]
diff --git a/tests/topotests/bgp_recursive_route_ebgp_multi_hop/test_bgp_recursive_route_ebgp_multi_hop.py b/tests/topotests/bgp_recursive_route_ebgp_multi_hop/test_bgp_recursive_route_ebgp_multi_hop.py
index 320c7eb78..918c16e34 100644
--- a/tests/topotests/bgp_recursive_route_ebgp_multi_hop/test_bgp_recursive_route_ebgp_multi_hop.py
+++ b/tests/topotests/bgp_recursive_route_ebgp_multi_hop/test_bgp_recursive_route_ebgp_multi_hop.py
@@ -89,14 +89,6 @@ from lib.topojson import build_topo_from_json, build_config_from_json
 pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
 
 
-# Reading the data from JSON File for topology and configuration creation
-jsonFile = "{}/bgp_recursive_route_ebgp_multi_hop.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    logger.info("Could not read file:", jsonFile)
-
 # Global variables
 BGP_CONVERGENCE = False
 KEEP_ALIVE_TIMER = 2
@@ -124,21 +116,6 @@ Loopabck_IP = {
 }
 
 
-class CreateTopo(Topo):
-    """
-    Test BasicTopo - topology 1
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function"""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
@@ -153,7 +130,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/bgp_recursive_route_ebgp_multi_hop.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/bgp_reject_as_sets/test_bgp_reject_as_sets.py b/tests/topotests/bgp_reject_as_sets/test_bgp_reject_as_sets.py
index f13b068d9..271db0a7c 100644
--- a/tests/topotests/bgp_reject_as_sets/test_bgp_reject_as_sets.py
+++ b/tests/topotests/bgp_reject_as_sets/test_bgp_reject_as_sets.py
@@ -53,24 +53,21 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    for routern in range(1, 4):
+        tgen.add_router("r{}".format(routern))
 
-        for routern in range(1, 4):
-            tgen.add_router("r{}".format(routern))
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
-
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_rfapi_basic_sanity/customize.py b/tests/topotests/bgp_rfapi_basic_sanity/customize.py
index 9166c57df..3cf53a184 100644
--- a/tests/topotests/bgp_rfapi_basic_sanity/customize.py
+++ b/tests/topotests/bgp_rfapi_basic_sanity/customize.py
@@ -81,35 +81,31 @@ CWD = os.path.dirname(os.path.realpath(__file__))
 TEST = os.path.basename(CWD)
 
 
-class ThisTestTopo(Topo):
-    "Test topology builder"
-
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
-
-        # This function only purpose is to define allocation and relationship
-        # between routers, switches and hosts.
-        #
-        # Create P/PE routers
-        tgen.add_router("r1")
-        for routern in range(2, 5):
-            tgen.add_router("r{}".format(routern))
-        # Create a switch with just one router connected to it to simulate a
-        # empty network.
-        switch = {}
-        switch[0] = tgen.add_switch("sw0")
-        switch[0].add_link(tgen.gears["r1"], nodeif="r1-eth0")
-        switch[0].add_link(tgen.gears["r2"], nodeif="r2-eth0")
-
-        switch[1] = tgen.add_switch("sw1")
-        switch[1].add_link(tgen.gears["r2"], nodeif="r2-eth1")
-        switch[1].add_link(tgen.gears["r3"], nodeif="r3-eth0")
-        switch[1].add_link(tgen.gears["r4"], nodeif="r4-eth0")
-
-        switch[2] = tgen.add_switch("sw2")
-        switch[2].add_link(tgen.gears["r2"], nodeif="r2-eth2")
-        switch[2].add_link(tgen.gears["r3"], nodeif="r3-eth1")
+def build_topo(tgen):
+    "Build function"
+
+    # This function only purpose is to define allocation and relationship
+    # between routers, switches and hosts.
+    #
+    # Create P/PE routers
+    tgen.add_router("r1")
+    for routern in range(2, 5):
+        tgen.add_router("r{}".format(routern))
+    # Create a switch with just one router connected to it to simulate a
+    # empty network.
+    switch = {}
+    switch[0] = tgen.add_switch("sw0")
+    switch[0].add_link(tgen.gears["r1"], nodeif="r1-eth0")
+    switch[0].add_link(tgen.gears["r2"], nodeif="r2-eth0")
+
+    switch[1] = tgen.add_switch("sw1")
+    switch[1].add_link(tgen.gears["r2"], nodeif="r2-eth1")
+    switch[1].add_link(tgen.gears["r3"], nodeif="r3-eth0")
+    switch[1].add_link(tgen.gears["r4"], nodeif="r4-eth0")
+
+    switch[2] = tgen.add_switch("sw2")
+    switch[2].add_link(tgen.gears["r2"], nodeif="r2-eth2")
+    switch[2].add_link(tgen.gears["r3"], nodeif="r3-eth1")
 
 
 def ltemplatePreRouterStartHook():
diff --git a/tests/topotests/bgp_rmap_extcommunity_none/test_bgp_rmap_extcommunity_none.py b/tests/topotests/bgp_rmap_extcommunity_none/test_bgp_rmap_extcommunity_none.py
index 3c11ba74c..d2a602f9a 100644
--- a/tests/topotests/bgp_rmap_extcommunity_none/test_bgp_rmap_extcommunity_none.py
+++ b/tests/topotests/bgp_rmap_extcommunity_none/test_bgp_rmap_extcommunity_none.py
@@ -41,25 +41,21 @@ sys.path.append(os.path.join(CWD, "../"))
 from lib import topotest
 from lib.topogen import Topogen, TopoRouter, get_topogen
 from lib.topolog import logger
-from mininet.topo import Topo
 
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    for routern in range(1, 3):
+        tgen.add_router("r{}".format(routern))
 
-        for routern in range(1, 3):
-            tgen.add_router("r{}".format(routern))
-
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_route_aggregation/test_bgp_aggregation.py b/tests/topotests/bgp_route_aggregation/test_bgp_aggregation.py
index 8297085ff..007e640f5 100644
--- a/tests/topotests/bgp_route_aggregation/test_bgp_aggregation.py
+++ b/tests/topotests/bgp_route_aggregation/test_bgp_aggregation.py
@@ -70,16 +70,8 @@ from lib.bgp import (
 )
 from lib.topojson import build_topo_from_json, build_config_from_json
 
-pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
-
 
-# Reading the data from JSON File for topology and configuration creation
-jsonFile = "{}/bgp_aggregation.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    logger.info("Could not read file:", jsonFile)
+pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
 
 # Global variables
 BGP_CONVERGENCE = False
@@ -113,21 +105,6 @@ COMMUNITY = [
 ]
 
 
-class CreateTopo(Topo):
-    """
-    Test BasicTopo - topology 1
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function"""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
@@ -142,7 +119,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/bgp_aggregation.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/bgp_route_map/test_route_map_topo1.py b/tests/topotests/bgp_route_map/test_route_map_topo1.py
index 17058d178..ba4456e71 100644
--- a/tests/topotests/bgp_route_map/test_route_map_topo1.py
+++ b/tests/topotests/bgp_route_map/test_route_map_topo1.py
@@ -115,13 +115,6 @@ TC_38:
 bgp_convergence = False
 BGP_CONVERGENCE = False
 ADDR_TYPES = check_address_types()
-# Reading the data from JSON File for topology and configuration creation
-jsonFile = "{}/bgp_route_map_topo1.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 
 # Global variables
 bgp_convergence = False
@@ -131,22 +124,6 @@ NEXT_HOP = {"ipv4": "10.0.0.2", "ipv6": "fd00::2"}
 ADDR_TYPES = check_address_types()
 
 
-class CreateTopo(Topo):
-    """
-    Test topology builder
-
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function"""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
@@ -161,7 +138,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/bgp_route_map_topo1.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/bgp_route_map/test_route_map_topo2.py b/tests/topotests/bgp_route_map/test_route_map_topo2.py
index d4b145e81..ca05ba45d 100644
--- a/tests/topotests/bgp_route_map/test_route_map_topo2.py
+++ b/tests/topotests/bgp_route_map/test_route_map_topo2.py
@@ -147,17 +147,8 @@ from lib.bgp import (
 )
 from lib.topojson import build_topo_from_json, build_config_from_json
 
-pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
-
-
-# Reading the data from JSON File for topology and configuration creation
-jsonFile = "{}/bgp_route_map_topo2.json".format(CWD)
 
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
+pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
 
 # Global variables
 # Global variables
@@ -169,21 +160,6 @@ BGP_CONVERGENCE = False
 ADDR_TYPES = check_address_types()
 
 
-class BGPRmapTopo(Topo):
-    """BGPRmapTopo.
-
-    BGPRmap topology 1
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology and configuration from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """setup_module.
 
@@ -197,7 +173,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(BGPRmapTopo, mod.__name__)
+    json_file = "{}/bgp_route_map_topo2.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/bgp_rr_ibgp/test_bgp_rr_ibgp_topo1.py b/tests/topotests/bgp_rr_ibgp/test_bgp_rr_ibgp_topo1.py
index 72c25a3c6..d40ea2ed8 100644
--- a/tests/topotests/bgp_rr_ibgp/test_bgp_rr_ibgp_topo1.py
+++ b/tests/topotests/bgp_rr_ibgp/test_bgp_rr_ibgp_topo1.py
@@ -49,48 +49,37 @@ from lib.topolog import logger
 # Required to instantiate the topology builder class.
 from lib.micronet_compat import Topo
 
-pytestmark = [pytest.mark.bgpd]
-
 
-#####################################################
-##
-##   Network Topology Definition
-##
-#####################################################
-
-
-class NetworkTopo(Topo):
-    "BGP_RR_IBGP Topology 1"
+pytestmark = [pytest.mark.bgpd]
 
-    def build(self, **_opts):
-        "Build function"
 
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    "Build function"
 
-        tgen.add_router("tor1")
-        tgen.add_router("tor2")
-        tgen.add_router("spine1")
+    tgen.add_router("tor1")
+    tgen.add_router("tor2")
+    tgen.add_router("spine1")
 
-        # First switch is for a dummy interface (for local network)
-        # on tor1
-        # 192.168.1.0/24
-        switch = tgen.add_switch("sw1")
-        switch.add_link(tgen.gears["tor1"])
+    # First switch is for a dummy interface (for local network)
+    # on tor1
+    # 192.168.1.0/24
+    switch = tgen.add_switch("sw1")
+    switch.add_link(tgen.gears["tor1"])
 
-        # 192.168.2.0/24 - tor1 <-> spine1 connection
-        switch = tgen.add_switch("sw2")
-        switch.add_link(tgen.gears["tor1"])
-        switch.add_link(tgen.gears["spine1"])
+    # 192.168.2.0/24 - tor1 <-> spine1 connection
+    switch = tgen.add_switch("sw2")
+    switch.add_link(tgen.gears["tor1"])
+    switch.add_link(tgen.gears["spine1"])
 
-        # 3rd switch is for a dummy interface (for local netwokr)
-        # 192.168.3.0/24 - tor2
-        switch = tgen.add_switch("sw3")
-        switch.add_link(tgen.gears["tor2"])
+    # 3rd switch is for a dummy interface (for local netwokr)
+    # 192.168.3.0/24 - tor2
+    switch = tgen.add_switch("sw3")
+    switch.add_link(tgen.gears["tor2"])
 
-        # 192.168.4.0/24 - tor2 <-> spine1 connection
-        switch = tgen.add_switch("sw4")
-        switch.add_link(tgen.gears["tor2"])
-        switch.add_link(tgen.gears["spine1"])
+    # 192.168.4.0/24 - tor2 <-> spine1 connection
+    switch = tgen.add_switch("sw4")
+    switch.add_link(tgen.gears["tor2"])
+    switch.add_link(tgen.gears["spine1"])
 
 
 #####################################################
@@ -102,7 +91,7 @@ class NetworkTopo(Topo):
 
 def setup_module(module):
     "Setup topology"
-    tgen = Topogen(NetworkTopo, module.__name__)
+    tgen = Topogen(build_topo, module.__name__)
     tgen.start_topology()
 
     # This is a sample of configuration loading.
diff --git a/tests/topotests/bgp_sender_as_path_loop_detection/test_bgp_sender-as-path-loop-detection.py b/tests/topotests/bgp_sender_as_path_loop_detection/test_bgp_sender-as-path-loop-detection.py
index 526e1202d..9d3c3a765 100644
--- a/tests/topotests/bgp_sender_as_path_loop_detection/test_bgp_sender-as-path-loop-detection.py
+++ b/tests/topotests/bgp_sender_as_path_loop_detection/test_bgp_sender-as-path-loop-detection.py
@@ -47,24 +47,21 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    for routern in range(1, 4):
+        tgen.add_router("r{}".format(routern))
 
-        for routern in range(1, 4):
-            tgen.add_router("r{}".format(routern))
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
-
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_set_local_preference_add_subtract/test_bgp_set_local-preference_add_subtract.py b/tests/topotests/bgp_set_local_preference_add_subtract/test_bgp_set_local-preference_add_subtract.py
index 531e1814a..0ef5f61d9 100644
--- a/tests/topotests/bgp_set_local_preference_add_subtract/test_bgp_set_local-preference_add_subtract.py
+++ b/tests/topotests/bgp_set_local_preference_add_subtract/test_bgp_set_local-preference_add_subtract.py
@@ -47,21 +47,18 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    for routern in range(1, 4):
+        tgen.add_router("r{}".format(routern))
 
-        for routern in range(1, 4):
-            tgen.add_router("r{}".format(routern))
-
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_snmp_mplsl3vpn/test_bgp_snmp_mplsvpn.py b/tests/topotests/bgp_snmp_mplsl3vpn/test_bgp_snmp_mplsvpn.py
index 37486f1d7..7f58c65ab 100755
--- a/tests/topotests/bgp_snmp_mplsl3vpn/test_bgp_snmp_mplsvpn.py
+++ b/tests/topotests/bgp_snmp_mplsl3vpn/test_bgp_snmp_mplsvpn.py
@@ -50,75 +50,71 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd, pytest.mark.isisd, pytest.mark.snmp]
 
 
-class TemplateTopo(Topo):
-    "Test topology builder"
-
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
-
-        # This function only purpose is to define allocation and relationship
-        # between routers, switches and hosts.
-        #
-        #
-        # Create routers
-        tgen.add_router("r1")
-        tgen.add_router("r2")
-        tgen.add_router("r3")
-        tgen.add_router("r4")
-        tgen.add_router("ce1")
-        tgen.add_router("ce2")
-        tgen.add_router("ce3")
-        tgen.add_router("ce4")
-
-        # r1-r2
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
-
-        # r1-r3
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r3"])
-
-        # r1-r4
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r4"])
-
-        # r1-ce1
-        switch = tgen.add_switch("s4")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["ce1"])
-
-        # r1-ce3
-        switch = tgen.add_switch("s5")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["ce3"])
-
-        # r1-ce4
-        switch = tgen.add_switch("s6")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["ce4"])
-
-        # r1-dangling
-        switch = tgen.add_switch("s7")
-        switch.add_link(tgen.gears["r1"])
-
-        # r2-r3
-        switch = tgen.add_switch("s8")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
-
-        # r3-r4
-        switch = tgen.add_switch("s9")
-        switch.add_link(tgen.gears["r3"])
-        switch.add_link(tgen.gears["r4"])
-
-        # r4-ce2
-        switch = tgen.add_switch("s10")
-        switch.add_link(tgen.gears["r4"])
-        switch.add_link(tgen.gears["ce2"])
+def build_topo(tgen):
+    "Build function"
+
+    # This function only purpose is to define allocation and relationship
+    # between routers, switches and hosts.
+    #
+    #
+    # Create routers
+    tgen.add_router("r1")
+    tgen.add_router("r2")
+    tgen.add_router("r3")
+    tgen.add_router("r4")
+    tgen.add_router("ce1")
+    tgen.add_router("ce2")
+    tgen.add_router("ce3")
+    tgen.add_router("ce4")
+
+    # r1-r2
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
+
+    # r1-r3
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r3"])
+
+    # r1-r4
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r4"])
+
+    # r1-ce1
+    switch = tgen.add_switch("s4")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["ce1"])
+
+    # r1-ce3
+    switch = tgen.add_switch("s5")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["ce3"])
+
+    # r1-ce4
+    switch = tgen.add_switch("s6")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["ce4"])
+
+    # r1-dangling
+    switch = tgen.add_switch("s7")
+    switch.add_link(tgen.gears["r1"])
+
+    # r2-r3
+    switch = tgen.add_switch("s8")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
+
+    # r3-r4
+    switch = tgen.add_switch("s9")
+    switch.add_link(tgen.gears["r3"])
+    switch.add_link(tgen.gears["r4"])
+
+    # r4-ce2
+    switch = tgen.add_switch("s10")
+    switch.add_link(tgen.gears["r4"])
+    switch.add_link(tgen.gears["ce2"])
 
 
 def setup_module(mod):
@@ -131,7 +127,7 @@ def setup_module(mod):
         pytest.skip(error_msg)
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     # ... and here it calls Mininet initialization functions.
     tgen.start_topology()
 
diff --git a/tests/topotests/bgp_srv6l3vpn_to_bgp_vrf/test_bgp_srv6l3vpn_to_bgp_vrf.py b/tests/topotests/bgp_srv6l3vpn_to_bgp_vrf/test_bgp_srv6l3vpn_to_bgp_vrf.py
index a50151ab2..60e419ab1 100755
--- a/tests/topotests/bgp_srv6l3vpn_to_bgp_vrf/test_bgp_srv6l3vpn_to_bgp_vrf.py
+++ b/tests/topotests/bgp_srv6l3vpn_to_bgp_vrf/test_bgp_srv6l3vpn_to_bgp_vrf.py
@@ -42,7 +42,7 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class Topology(Topo):
+def build_topo(tgen):
     """
       CE1     CE3      CE5
     (eth0)  (eth0)   (eth0)
@@ -79,24 +79,22 @@ class Topology(Topo):
       (eth0)      (eth0)      (eth0)
         CE2         CE4         CE6
     """
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
-        tgen.add_router("r1")
-        tgen.add_router("r2")
-        tgen.add_router("ce1")
-        tgen.add_router("ce2")
-        tgen.add_router("ce3")
-        tgen.add_router("ce4")
-        tgen.add_router("ce5")
-        tgen.add_router("ce6")
-
-        tgen.add_link(tgen.gears["r1"], tgen.gears["r2"], "eth0", "eth0")
-        tgen.add_link(tgen.gears["ce1"], tgen.gears["r1"], "eth0", "eth1")
-        tgen.add_link(tgen.gears["ce2"], tgen.gears["r2"], "eth0", "eth1")
-        tgen.add_link(tgen.gears["ce3"], tgen.gears["r1"], "eth0", "eth2")
-        tgen.add_link(tgen.gears["ce4"], tgen.gears["r2"], "eth0", "eth2")
-        tgen.add_link(tgen.gears["ce5"], tgen.gears["r1"], "eth0", "eth3")
-        tgen.add_link(tgen.gears["ce6"], tgen.gears["r2"], "eth0", "eth3")
+    tgen.add_router("r1")
+    tgen.add_router("r2")
+    tgen.add_router("ce1")
+    tgen.add_router("ce2")
+    tgen.add_router("ce3")
+    tgen.add_router("ce4")
+    tgen.add_router("ce5")
+    tgen.add_router("ce6")
+
+    tgen.add_link(tgen.gears["r1"], tgen.gears["r2"], "eth0", "eth0")
+    tgen.add_link(tgen.gears["ce1"], tgen.gears["r1"], "eth0", "eth1")
+    tgen.add_link(tgen.gears["ce2"], tgen.gears["r2"], "eth0", "eth1")
+    tgen.add_link(tgen.gears["ce3"], tgen.gears["r1"], "eth0", "eth2")
+    tgen.add_link(tgen.gears["ce4"], tgen.gears["r2"], "eth0", "eth2")
+    tgen.add_link(tgen.gears["ce5"], tgen.gears["r1"], "eth0", "eth3")
+    tgen.add_link(tgen.gears["ce6"], tgen.gears["r2"], "eth0", "eth3")
 
 
 def setup_module(mod):
@@ -104,7 +102,7 @@ def setup_module(mod):
     if result is not True:
         pytest.skip("Kernel requirements are not met")
 
-    tgen = Topogen(Topology, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
     router_list = tgen.routers()
     for rname, router in tgen.routers().items():
diff --git a/tests/topotests/bgp_suppress_fib/test_bgp_suppress_fib.py b/tests/topotests/bgp_suppress_fib/test_bgp_suppress_fib.py
index 3e421ad5c..2c14ad9de 100644
--- a/tests/topotests/bgp_suppress_fib/test_bgp_suppress_fib.py
+++ b/tests/topotests/bgp_suppress_fib/test_bgp_suppress_fib.py
@@ -43,24 +43,21 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    for routern in range(1, 4):
+        tgen.add_router("r{}".format(routern))
 
-        for routern in range(1, 4):
-            tgen.add_router("r{}".format(routern))
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
-
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_tcp_mss/test_bgp_tcp_mss.py b/tests/topotests/bgp_tcp_mss/test_bgp_tcp_mss.py
index 7ca30daf4..db90bbd5d 100644
--- a/tests/topotests/bgp_tcp_mss/test_bgp_tcp_mss.py
+++ b/tests/topotests/bgp_tcp_mss/test_bgp_tcp_mss.py
@@ -54,20 +54,17 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    for routern in range(1, 3):
+        tgen.add_router("r{}".format(routern))
 
-        for routern in range(1, 3):
-            tgen.add_router("r{}".format(routern))
-
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_update_delay/test_bgp_update_delay.py b/tests/topotests/bgp_update_delay/test_bgp_update_delay.py
index a936d44d1..31a887b6c 100644
--- a/tests/topotests/bgp_update_delay/test_bgp_update_delay.py
+++ b/tests/topotests/bgp_update_delay/test_bgp_update_delay.py
@@ -76,32 +76,30 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class TemplateTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
-
-        for routern in range(1, 6):
-            tgen.add_router("r{}".format(routern))
+CWD = os.path.dirname(os.path.realpath(__file__))
+def build_topo(tgen):
+    for routern in range(1, 6):
+        tgen.add_router("r{}".format(routern))
 
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
 
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r4"])
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r4"])
 
-        switch = tgen.add_switch("s4")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r5"])
+    switch = tgen.add_switch("s4")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r5"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_vrf_dynamic_route_leak/test_bgp_vrf_dynamic_route_leak_topo1.py b/tests/topotests/bgp_vrf_dynamic_route_leak/test_bgp_vrf_dynamic_route_leak_topo1.py
index 63e724cc5..b2e2250a9 100644
--- a/tests/topotests/bgp_vrf_dynamic_route_leak/test_bgp_vrf_dynamic_route_leak_topo1.py
+++ b/tests/topotests/bgp_vrf_dynamic_route_leak/test_bgp_vrf_dynamic_route_leak_topo1.py
@@ -81,16 +81,8 @@ from lib.bgp import (
 )
 from lib.topojson import build_topo_from_json, build_config_from_json
 
-pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
-
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/bgp_vrf_dynamic_route_leak_topo1.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
+pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
 
 # Global variables
 NETWORK1_1 = {"ipv4": "11.11.11.1/32", "ipv6": "11:11::1/128"}
@@ -125,21 +117,6 @@ LOOPBACK_2 = {
 PREFERRED_NEXT_HOP = "global"
 
 
-class CreateTopo(Topo):
-    """
-    Test BasicTopo - topology 1
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function"""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
@@ -147,7 +124,6 @@ def setup_module(mod):
     * `mod`: module name
     """
 
-    global topo
     testsuite_run_time = time.asctime(time.localtime(time.time()))
     logger.info("Testsuite start time: {}".format(testsuite_run_time))
     logger.info("=" * 40)
@@ -155,7 +131,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/bgp_vrf_dynamic_route_leak_topo1.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/bgp_vrf_dynamic_route_leak/test_bgp_vrf_dynamic_route_leak_topo2.py b/tests/topotests/bgp_vrf_dynamic_route_leak/test_bgp_vrf_dynamic_route_leak_topo2.py
index 1241a37cf..8e3e32fc8 100644
--- a/tests/topotests/bgp_vrf_dynamic_route_leak/test_bgp_vrf_dynamic_route_leak_topo2.py
+++ b/tests/topotests/bgp_vrf_dynamic_route_leak/test_bgp_vrf_dynamic_route_leak_topo2.py
@@ -97,19 +97,11 @@ NETWORK3_4 = {"ipv4": "50.50.50.50/32", "ipv6": "50:50::50/128"}
 PREFERRED_NEXT_HOP = "global"
 
 
-class CreateTopo(Topo):
-    """
-    Test BasicTopo - topology 1
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function"""
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    """Build function"""
 
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
+    # Building topology from json file
+    build_topo_from_json(tgen, topo)
 
 
 def setup_module(mod):
@@ -127,7 +119,7 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/bgp_vrf_lite_ipv6_rtadv/test_bgp_vrf_lite_ipv6_rtadv.py b/tests/topotests/bgp_vrf_lite_ipv6_rtadv/test_bgp_vrf_lite_ipv6_rtadv.py
index b818816d9..5d6a5859c 100644
--- a/tests/topotests/bgp_vrf_lite_ipv6_rtadv/test_bgp_vrf_lite_ipv6_rtadv.py
+++ b/tests/topotests/bgp_vrf_lite_ipv6_rtadv/test_bgp_vrf_lite_ipv6_rtadv.py
@@ -50,20 +50,16 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd]
 
 
-class BGPIPV6RTADVVRFTopo(Topo):
-    "Test topology builder"
+def build_topo(tgen):
+    "Build function"
 
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+    # Create 2 routers.
+    tgen.add_router("r1")
+    tgen.add_router("r2")
 
-        # Create 2 routers.
-        tgen.add_router("r1")
-        tgen.add_router("r2")
-
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
 
 def setup_module(mod):
@@ -74,7 +70,7 @@ def setup_module(mod):
     if result is not True:
         pytest.skip("Kernel requirements are not met")
 
-    tgen = Topogen(BGPIPV6RTADVVRFTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/bgp_vrf_netns/test_bgp_vrf_netns_topo.py b/tests/topotests/bgp_vrf_netns/test_bgp_vrf_netns_topo.py
index 9c4c78bf1..d0011f9df 100644
--- a/tests/topotests/bgp_vrf_netns/test_bgp_vrf_netns_topo.py
+++ b/tests/topotests/bgp_vrf_netns/test_bgp_vrf_netns_topo.py
@@ -57,25 +57,19 @@ CustomizeVrfWithNetns = True
 #####################################################
 
 
-class BGPVRFNETNSTopo1(Topo):
-    "BGP EBGP VRF NETNS Topology 1"
+def build_topo(tgen):
+    tgen.add_router("r1")
 
-    def build(self, **_opts):
-        tgen = get_topogen(self)
+    # Setup Switches
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
 
-        # Setup Routers
-        tgen.add_router("r1")
-
-        # Setup Switches
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-
-        # Add eBGP ExaBGP neighbors
-        peer_ip = "10.0.1.101"
-        peer_route = "via 10.0.1.1"
-        peer = tgen.add_exabgp_peer("peer1", ip=peer_ip, defaultRoute=peer_route)
-        switch = tgen.gears["s1"]
-        switch.add_link(peer)
+    # Add eBGP ExaBGP neighbors
+    peer_ip = "10.0.1.101"
+    peer_route = "via 10.0.1.1"
+    peer = tgen.add_exabgp_peer("peer1", ip=peer_ip, defaultRoute=peer_route)
+    switch = tgen.gears["s1"]
+    switch.add_link(peer)
 
 
 #####################################################
@@ -86,7 +80,7 @@ class BGPVRFNETNSTopo1(Topo):
 
 
 def setup_module(module):
-    tgen = Topogen(BGPVRFNETNSTopo1, module.__name__)
+    tgen = Topogen(build_topo, module.__name__)
     tgen.start_topology()
 
     # Get r1 reference
diff --git a/tests/topotests/bgp_vrf_route_leak_basic/test_bgp-vrf-route-leak-basic.py b/tests/topotests/bgp_vrf_route_leak_basic/test_bgp-vrf-route-leak-basic.py
index 7ab2c608b..66a52841f 100644
--- a/tests/topotests/bgp_vrf_route_leak_basic/test_bgp-vrf-route-leak-basic.py
+++ b/tests/topotests/bgp_vrf_route_leak_basic/test_bgp-vrf-route-leak-basic.py
@@ -41,21 +41,20 @@ from lib.topolog import logger
 
 from lib.micronet_compat import Topo
 
+
 pytestmark = [pytest.mark.bgpd]
 
 
-class BGPVRFTopo(Topo):
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    "Build function"
 
-        for routern in range(1, 2):
-            tgen.add_router("r{}".format(routern))
+    for routern in range(1, 2):
+        tgen.add_router("r{}".format(routern))
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(BGPVRFTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     # For all registered routers, load the zebra configuration file
diff --git a/tests/topotests/config_timing/test_config_timing.py b/tests/topotests/config_timing/test_config_timing.py
index 54dca32e1..b68f52bbd 100644
--- a/tests/topotests/config_timing/test_config_timing.py
+++ b/tests/topotests/config_timing/test_config_timing.py
@@ -49,16 +49,14 @@ from lib.micronet_compat import Topo
 
 pytestmark = [pytest.mark.staticd]
 
-class TimingTopo(Topo):
-    def build(self, *_args, **_opts):
-        tgen = get_topogen(self)
-        tgen.add_router("r1")
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
+def build_topo(tgen):
+    tgen.add_router("r1")
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
 
 
 def setup_module(mod):
-    tgen = Topogen(TimingTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/eigrp_topo1/test_eigrp_topo1.py b/tests/topotests/eigrp_topo1/test_eigrp_topo1.py
index 982d3f0fa..f97b1f2da 100644
--- a/tests/topotests/eigrp_topo1/test_eigrp_topo1.py
+++ b/tests/topotests/eigrp_topo1/test_eigrp_topo1.py
@@ -55,36 +55,29 @@ from lib.micronet_compat import Topo
 #####################################################
 
 
-class NetworkTopo(Topo):
-    "EIGRP Topology 1"
+def build_topo(tgen):
+    for routern in range(1, 4):
+        tgen.add_router("r{}".format(routern))
 
-    def build(self, **_opts):
-        "Build function"
+    # On main router
+    # First switch is for a dummy interface (for local network)
+    switch = tgen.add_switch("sw1")
+    switch.add_link(tgen.gears["r1"])
 
-        tgen = get_topogen(self)
+    # Switches for EIGRP
+    # switch 2 switch is for connection to EIGRP router
+    switch = tgen.add_switch("sw2")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
-        for routern in range(1, 4):
-            tgen.add_router("r{}".format(routern))
+    # switch 4 is stub on remote EIGRP router
+    switch = tgen.add_switch("sw4")
+    switch.add_link(tgen.gears["r3"])
 
-        # On main router
-        # First switch is for a dummy interface (for local network)
-        switch = tgen.add_switch("sw1")
-        switch.add_link(tgen.gears["r1"])
-
-        # Switches for EIGRP
-        # switch 2 switch is for connection to EIGRP router
-        switch = tgen.add_switch("sw2")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
-
-        # switch 4 is stub on remote EIGRP router
-        switch = tgen.add_switch("sw4")
-        switch.add_link(tgen.gears["r3"])
-
-        # switch 3 is between EIGRP routers
-        switch = tgen.add_switch("sw3")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
+    # switch 3 is between EIGRP routers
+    switch = tgen.add_switch("sw3")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
 
 
 #####################################################
@@ -96,7 +89,7 @@ class NetworkTopo(Topo):
 
 def setup_module(module):
     "Setup topology"
-    tgen = Topogen(NetworkTopo, module.__name__)
+    tgen = Topogen(build_topo, module.__name__)
     tgen.start_topology()
 
     # This is a sample of configuration loading.
diff --git a/tests/topotests/evpn_pim_1/test_evpn_pim_topo1.py b/tests/topotests/evpn_pim_1/test_evpn_pim_topo1.py
index e549d1acb..216494d4e 100644
--- a/tests/topotests/evpn_pim_1/test_evpn_pim_topo1.py
+++ b/tests/topotests/evpn_pim_1/test_evpn_pim_topo1.py
@@ -59,41 +59,34 @@ pytestmark = [pytest.mark.bgpd, pytest.mark.bgpd]
 #####################################################
 
 
-class NetworkTopo(Topo):
-    "evpn-pim Topology 1"
-
-    def build(self, **_opts):
-        "Build function"
-
-        tgen = get_topogen(self)
-
-        tgen.add_router("spine")
-        tgen.add_router("leaf1")
-        tgen.add_router("leaf2")
-        tgen.add_router("host1")
-        tgen.add_router("host2")
-
-        # On main router
-        # First switch is for a dummy interface (for local network)
-        # spine-eth0 is connected to leaf1-eth0
-        switch = tgen.add_switch("sw1")
-        switch.add_link(tgen.gears["spine"])
-        switch.add_link(tgen.gears["leaf1"])
-
-        # spine-eth1 is connected to leaf2-eth0
-        switch = tgen.add_switch("sw2")
-        switch.add_link(tgen.gears["spine"])
-        switch.add_link(tgen.gears["leaf2"])
-
-        # leaf1-eth1 is connected to host1-eth0
-        switch = tgen.add_switch("sw3")
-        switch.add_link(tgen.gears["leaf1"])
-        switch.add_link(tgen.gears["host1"])
-
-        # leaf2-eth1 is connected to host2-eth0
-        switch = tgen.add_switch("sw4")
-        switch.add_link(tgen.gears["leaf2"])
-        switch.add_link(tgen.gears["host2"])
+def build_topo(tgen):
+    tgen.add_router("spine")
+    tgen.add_router("leaf1")
+    tgen.add_router("leaf2")
+    tgen.add_router("host1")
+    tgen.add_router("host2")
+
+    # On main router
+    # First switch is for a dummy interface (for local network)
+    # spine-eth0 is connected to leaf1-eth0
+    switch = tgen.add_switch("sw1")
+    switch.add_link(tgen.gears["spine"])
+    switch.add_link(tgen.gears["leaf1"])
+
+    # spine-eth1 is connected to leaf2-eth0
+    switch = tgen.add_switch("sw2")
+    switch.add_link(tgen.gears["spine"])
+    switch.add_link(tgen.gears["leaf2"])
+
+    # leaf1-eth1 is connected to host1-eth0
+    switch = tgen.add_switch("sw3")
+    switch.add_link(tgen.gears["leaf1"])
+    switch.add_link(tgen.gears["host1"])
+
+    # leaf2-eth1 is connected to host2-eth0
+    switch = tgen.add_switch("sw4")
+    switch.add_link(tgen.gears["leaf2"])
+    switch.add_link(tgen.gears["host2"])
 
 
 #####################################################
@@ -105,7 +98,7 @@ class NetworkTopo(Topo):
 
 def setup_module(module):
     "Setup topology"
-    tgen = Topogen(NetworkTopo, module.__name__)
+    tgen = Topogen(build_topo, module.__name__)
     tgen.start_topology()
 
     leaf1 = tgen.gears["leaf1"]
diff --git a/tests/topotests/evpn_type5_test_topo1/test_evpn_type5_chaos_topo1.py b/tests/topotests/evpn_type5_test_topo1/test_evpn_type5_chaos_topo1.py
index d72b28e84..83c415c0f 100644
--- a/tests/topotests/evpn_type5_test_topo1/test_evpn_type5_chaos_topo1.py
+++ b/tests/topotests/evpn_type5_test_topo1/test_evpn_type5_chaos_topo1.py
@@ -85,16 +85,8 @@ from lib.bgp import (
 )
 from lib.topojson import build_topo_from_json, build_config_from_json
 
-pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
-
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/evpn_type5_chaos_topo1.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
+pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
 
 # Reading the data from JSON File for topology creation
 # Global variables
@@ -139,21 +131,6 @@ BRCTL = {
 }
 
 
-class CreateTopo(Topo):
-    """
-    Test BasicTopo - topology 1
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function"""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
@@ -161,7 +138,6 @@ def setup_module(mod):
     * `mod`: module name
     """
 
-    global topo
     testsuite_run_time = time.asctime(time.localtime(time.time()))
     logger.info("Testsuite start time: {}".format(testsuite_run_time))
     logger.info("=" * 40)
@@ -169,7 +145,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/evpn_type5_chaos_topo1.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/evpn_type5_test_topo1/test_evpn_type5_topo1.py b/tests/topotests/evpn_type5_test_topo1/test_evpn_type5_topo1.py
index fda39be91..3a101b453 100644
--- a/tests/topotests/evpn_type5_test_topo1/test_evpn_type5_topo1.py
+++ b/tests/topotests/evpn_type5_test_topo1/test_evpn_type5_topo1.py
@@ -142,19 +142,8 @@ BRCTL = {
 }
 
 
-class CreateTopo(Topo):
-    """
-    Test BasicTopo - topology 1
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function"""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
+def build_topo(tgen):
+    build_topo_from_json(tgen, topo)
 
 
 def setup_module(mod):
@@ -172,7 +161,7 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/example_test/test_template.py b/tests/topotests/example_test/test_template.py
index 534dd998d..7bd434d75 100644
--- a/tests/topotests/example_test/test_template.py
+++ b/tests/topotests/example_test/test_template.py
@@ -30,19 +30,10 @@ import os
 import sys
 import pytest
 
-# Save the Current Working Directory to find configuration files.
-CWD = os.path.dirname(os.path.realpath(__file__))
-sys.path.append(os.path.join(CWD, "../"))
-
-# pylint: disable=C0413
 # Import topogen and topotest helpers
-from lib import topotest
 from lib.topogen import Topogen, TopoRouter, get_topogen
 from lib.topolog import logger
 
-# Required to instantiate the topology builder class.
-from lib.micronet_compat import Topo
-
 
 # TODO: select markers based on daemons used during test
 # pytest module level markers
@@ -56,37 +47,40 @@ pytestmark = [
 """
 
 
-class TemplateTopo(Topo):
-    "Test topology builder"
+def build_topo(tgen):
+    "Build function"
 
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+    # Create 2 routers
+    for routern in range(1, 3):
+        tgen.add_router("r{}".format(routern))
 
-        # This function only purpose is to define allocation and relationship
-        # between routers, switches and hosts.
-        #
-        # Example
-        #
-        # Create 2 routers
-        for routern in range(1, 3):
-            tgen.add_router("r{}".format(routern))
+    # Create a switch with just one router connected to it to simulate a
+    # empty network.
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
 
-        # Create a switch with just one router connected to it to simulate a
-        # empty network.
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-
-        # Create a connection between r1 and r2
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    # Create a connection between r1 and r2
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
+
+
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
+
+    # The basic topology above could also have be more easily specified using a
+    # dictionary, remove the build_topo function and use the following instead:
+    #
+    # topodef = {
+    #     "s1": "r1"
+    #     "s2": ("r1", "r2")
+    # }
+    # tgen = Topogen(topodef, mod.__name__)
+
     # ... and here it calls initialization functions.
     tgen.start_topology()
 
@@ -94,6 +88,7 @@ def setup_module(mod):
     router_list = tgen.routers()
 
     # For all registred routers, load the zebra configuration file
+    # CWD = os.path.dirname(os.path.realpath(__file__))
     for rname, router in router_list.items():
         router.load_config(
             TopoRouter.RD_ZEBRA,
diff --git a/tests/topotests/example_topojson_test/test_topo_json_multiple_links/test_example_topojson_multiple_links.py b/tests/topotests/example_topojson_test/test_topo_json_multiple_links/test_example_topojson_multiple_links.py
index b08861637..11b58301d 100755
--- a/tests/topotests/example_topojson_test/test_topo_json_multiple_links/test_example_topojson_multiple_links.py
+++ b/tests/topotests/example_topojson_test/test_topo_json_multiple_links/test_example_topojson_multiple_links.py
@@ -79,27 +79,19 @@ bgp_convergence = False
 input_dict = {}
 
 
-class TemplateTopo(Topo):
-    """
-    Test topology builder
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    "Build function"
 
-        # This function only purpose is to create topology
-        # as defined in input json file.
-        #
-        # Example
-        #
-        # Creating 2 routers having 2 links in between,
-        # one is used to establised BGP neighborship
+    # This function only purpose is to create topology
+    # as defined in input json file.
+    #
+    # Example
+    #
+    # Creating 2 routers having 2 links in between,
+    # one is used to establised BGP neighborship
 
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
+    # Building topology from json file
+    build_topo_from_json(tgen, topo)
 
 
 def setup_module(mod):
@@ -116,7 +108,7 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/example_topojson_test/test_topo_json_single_link/test_example_topojson.py b/tests/topotests/example_topojson_test/test_topo_json_single_link/test_example_topojson.py
index 4b13dce7d..82cc9bd94 100755
--- a/tests/topotests/example_topojson_test/test_topo_json_single_link/test_example_topojson.py
+++ b/tests/topotests/example_topojson_test/test_topo_json_single_link/test_example_topojson.py
@@ -79,27 +79,19 @@ bgp_convergence = False
 input_dict = {}
 
 
-class TemplateTopo(Topo):
-    """
-    Test topology builder
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    "Build function"
 
-        # This function only purpose is to create topology
-        # as defined in input json file.
-        #
-        # Example
-        #
-        # Creating 2 routers having single links in between,
-        # which is used to establised BGP neighborship
+    # This function only purpose is to create topology
+    # as defined in input json file.
+    #
+    # Example
+    #
+    # Creating 2 routers having single links in between,
+    # which is used to establised BGP neighborship
 
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
+    # Building topology from json file
+    build_topo_from_json(tgen, topo)
 
 
 def setup_module(mod):
@@ -116,7 +108,7 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/example_topojson_test/test_topo_json_single_link_loopback/test_example_topojson.py b/tests/topotests/example_topojson_test/test_topo_json_single_link_loopback/test_example_topojson.py
index 07d13cb71..9ab9f77f0 100755
--- a/tests/topotests/example_topojson_test/test_topo_json_single_link_loopback/test_example_topojson.py
+++ b/tests/topotests/example_topojson_test/test_topo_json_single_link_loopback/test_example_topojson.py
@@ -81,27 +81,19 @@ bgp_convergence = False
 input_dict = {}
 
 
-class TemplateTopo(Topo):
-    """
-    Test topology builder
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    "Build function"
 
-        # This function only purpose is to create topology
-        # as defined in input json file.
-        #
-        # Example
-        #
-        # Creating 2 routers having single links in between,
-        # which is used to establised BGP neighborship
+    # This function only purpose is to create topology
+    # as defined in input json file.
+    #
+    # Example
+    #
+    # Creating 2 routers having single links in between,
+    # which is used to establised BGP neighborship
 
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
+    # Building topology from json file
+    build_topo_from_json(tgen, topo)
 
 
 def setup_module(mod):
@@ -118,7 +110,7 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/isis_lfa_topo1/test_isis_lfa_topo1.py b/tests/topotests/isis_lfa_topo1/test_isis_lfa_topo1.py
index 5555b1dca..07391ec2b 100755
--- a/tests/topotests/isis_lfa_topo1/test_isis_lfa_topo1.py
+++ b/tests/topotests/isis_lfa_topo1/test_isis_lfa_topo1.py
@@ -164,7 +164,7 @@ def build_topo(tgen):
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/isis_lsp_bits_topo1/test_isis_lsp_bits_topo1.py b/tests/topotests/isis_lsp_bits_topo1/test_isis_lsp_bits_topo1.py
index df174e953..b86a2cf31 100755
--- a/tests/topotests/isis_lsp_bits_topo1/test_isis_lsp_bits_topo1.py
+++ b/tests/topotests/isis_lsp_bits_topo1/test_isis_lsp_bits_topo1.py
@@ -91,51 +91,47 @@ pytestmark = [pytest.mark.isisd]
 outputs = {}
 
 
-class TemplateTopo(Topo):
-    "Test topology builder"
+def build_topo(tgen):
+    "Build function"
 
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+    #
+    # Define FRR Routers
+    #
+    for router in ["rt1", "rt2", "rt3", "rt4", "rt5", "rt6"]:
+        tgen.add_router(router)
 
-        #
-        # Define FRR Routers
-        #
-        for router in ["rt1", "rt2", "rt3", "rt4", "rt5", "rt6"]:
-            tgen.add_router(router)
+    #
+    # Define connections
+    #
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["rt1"], nodeif="eth-sw1")
+    switch.add_link(tgen.gears["rt2"], nodeif="eth-sw1")
+    switch.add_link(tgen.gears["rt3"], nodeif="eth-sw1")
 
-        #
-        # Define connections
-        #
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["rt1"], nodeif="eth-sw1")
-        switch.add_link(tgen.gears["rt2"], nodeif="eth-sw1")
-        switch.add_link(tgen.gears["rt3"], nodeif="eth-sw1")
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["rt2"], nodeif="eth-rt4")
+    switch.add_link(tgen.gears["rt4"], nodeif="eth-rt2")
 
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["rt2"], nodeif="eth-rt4")
-        switch.add_link(tgen.gears["rt4"], nodeif="eth-rt2")
+    switch = tgen.add_switch("s4")
+    switch.add_link(tgen.gears["rt3"], nodeif="eth-rt5")
+    switch.add_link(tgen.gears["rt5"], nodeif="eth-rt3")
 
-        switch = tgen.add_switch("s4")
-        switch.add_link(tgen.gears["rt3"], nodeif="eth-rt5")
-        switch.add_link(tgen.gears["rt5"], nodeif="eth-rt3")
+    switch = tgen.add_switch("s6")
+    switch.add_link(tgen.gears["rt4"], nodeif="eth-rt5")
+    switch.add_link(tgen.gears["rt5"], nodeif="eth-rt4")
 
-        switch = tgen.add_switch("s6")
-        switch.add_link(tgen.gears["rt4"], nodeif="eth-rt5")
-        switch.add_link(tgen.gears["rt5"], nodeif="eth-rt4")
+    switch = tgen.add_switch("s7")
+    switch.add_link(tgen.gears["rt4"], nodeif="eth-rt6")
+    switch.add_link(tgen.gears["rt6"], nodeif="eth-rt4")
 
-        switch = tgen.add_switch("s7")
-        switch.add_link(tgen.gears["rt4"], nodeif="eth-rt6")
-        switch.add_link(tgen.gears["rt6"], nodeif="eth-rt4")
-
-        switch = tgen.add_switch("s8")
-        switch.add_link(tgen.gears["rt5"], nodeif="eth-rt6")
-        switch.add_link(tgen.gears["rt6"], nodeif="eth-rt5")
+    switch = tgen.add_switch("s8")
+    switch.add_link(tgen.gears["rt5"], nodeif="eth-rt6")
+    switch.add_link(tgen.gears["rt6"], nodeif="eth-rt5")
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/isis_rlfa_topo1/test_isis_rlfa_topo1.py b/tests/topotests/isis_rlfa_topo1/test_isis_rlfa_topo1.py
index e2cb080eb..39a03a3e9 100755
--- a/tests/topotests/isis_rlfa_topo1/test_isis_rlfa_topo1.py
+++ b/tests/topotests/isis_rlfa_topo1/test_isis_rlfa_topo1.py
@@ -166,7 +166,7 @@ def build_topo(tgen):
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/isis_snmp/test_isis_snmp.py b/tests/topotests/isis_snmp/test_isis_snmp.py
index 6ca5928fd..cb8705e5b 100755
--- a/tests/topotests/isis_snmp/test_isis_snmp.py
+++ b/tests/topotests/isis_snmp/test_isis_snmp.py
@@ -85,45 +85,41 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.isisd, pytest.mark.ldpd, pytest.mark.snmp]
 
 
-class TemplateTopo(Topo):
-    "Test topology builder"
+def build_topo(tgen):
+    "Build function"
 
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+    #
+    # Define FRR Routers
+    #
+    for router in ["ce3", "r1", "r2", "r3", "r4", "r5"]:
+        tgen.add_router(router)
 
-        #
-        # Define FRR Routers
-        #
-        for router in ["ce3", "r1", "r2", "r3", "r4", "r5"]:
-            tgen.add_router(router)
+    #
+    # Define connections
+    #
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r4"])
 
-        #
-        # Define connections
-        #
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r4"])
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r5"])
+    switch.add_link(tgen.gears["r2"])
 
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["r5"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["ce3"])
+    switch.add_link(tgen.gears["r3"])
 
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["ce3"])
-        switch.add_link(tgen.gears["r3"])
+    switch = tgen.add_switch("s4")
+    switch.add_link(tgen.gears["r4"])
+    switch.add_link(tgen.gears["r5"])
 
-        switch = tgen.add_switch("s4")
-        switch.add_link(tgen.gears["r4"])
-        switch.add_link(tgen.gears["r5"])
+    switch = tgen.add_switch("s5")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r3"])
 
-        switch = tgen.add_switch("s5")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r3"])
-
-        switch = tgen.add_switch("s6")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
+    switch = tgen.add_switch("s6")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
 
 
 def setup_module(mod):
@@ -135,7 +131,7 @@ def setup_module(mod):
         pytest.skip(error_msg)
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     # ... and here it calls Mininet initialization functions.
     tgen.start_topology()
 
diff --git a/tests/topotests/isis_sr_te_topo1/test_isis_sr_te_topo1.py b/tests/topotests/isis_sr_te_topo1/test_isis_sr_te_topo1.py
index 260457b67..c653d5286 100755
--- a/tests/topotests/isis_sr_te_topo1/test_isis_sr_te_topo1.py
+++ b/tests/topotests/isis_sr_te_topo1/test_isis_sr_te_topo1.py
@@ -99,64 +99,60 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd, pytest.mark.isisd, pytest.mark.pathd]
 
 
-class TemplateTopo(Topo):
-    "Test topology builder"
+def build_topo(tgen):
+    "Build function"
 
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+    #
+    # Define FRR Routers
+    #
+    for router in ["rt1", "rt2", "rt3", "rt4", "rt5", "rt6", "dst"]:
+        tgen.add_router(router)
 
-        #
-        # Define FRR Routers
-        #
-        for router in ["rt1", "rt2", "rt3", "rt4", "rt5", "rt6", "dst"]:
-            tgen.add_router(router)
+    #
+    # Define connections
+    #
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["rt1"], nodeif="eth-sw1")
+    switch.add_link(tgen.gears["rt2"], nodeif="eth-sw1")
+    switch.add_link(tgen.gears["rt3"], nodeif="eth-sw1")
 
-        #
-        # Define connections
-        #
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["rt1"], nodeif="eth-sw1")
-        switch.add_link(tgen.gears["rt2"], nodeif="eth-sw1")
-        switch.add_link(tgen.gears["rt3"], nodeif="eth-sw1")
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["rt2"], nodeif="eth-rt4-1")
+    switch.add_link(tgen.gears["rt4"], nodeif="eth-rt2-1")
 
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["rt2"], nodeif="eth-rt4-1")
-        switch.add_link(tgen.gears["rt4"], nodeif="eth-rt2-1")
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["rt2"], nodeif="eth-rt4-2")
+    switch.add_link(tgen.gears["rt4"], nodeif="eth-rt2-2")
 
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["rt2"], nodeif="eth-rt4-2")
-        switch.add_link(tgen.gears["rt4"], nodeif="eth-rt2-2")
+    switch = tgen.add_switch("s4")
+    switch.add_link(tgen.gears["rt3"], nodeif="eth-rt5-1")
+    switch.add_link(tgen.gears["rt5"], nodeif="eth-rt3-1")
 
-        switch = tgen.add_switch("s4")
-        switch.add_link(tgen.gears["rt3"], nodeif="eth-rt5-1")
-        switch.add_link(tgen.gears["rt5"], nodeif="eth-rt3-1")
+    switch = tgen.add_switch("s5")
+    switch.add_link(tgen.gears["rt3"], nodeif="eth-rt5-2")
+    switch.add_link(tgen.gears["rt5"], nodeif="eth-rt3-2")
 
-        switch = tgen.add_switch("s5")
-        switch.add_link(tgen.gears["rt3"], nodeif="eth-rt5-2")
-        switch.add_link(tgen.gears["rt5"], nodeif="eth-rt3-2")
+    switch = tgen.add_switch("s6")
+    switch.add_link(tgen.gears["rt4"], nodeif="eth-rt5")
+    switch.add_link(tgen.gears["rt5"], nodeif="eth-rt4")
 
-        switch = tgen.add_switch("s6")
-        switch.add_link(tgen.gears["rt4"], nodeif="eth-rt5")
-        switch.add_link(tgen.gears["rt5"], nodeif="eth-rt4")
+    switch = tgen.add_switch("s7")
+    switch.add_link(tgen.gears["rt4"], nodeif="eth-rt6")
+    switch.add_link(tgen.gears["rt6"], nodeif="eth-rt4")
 
-        switch = tgen.add_switch("s7")
-        switch.add_link(tgen.gears["rt4"], nodeif="eth-rt6")
-        switch.add_link(tgen.gears["rt6"], nodeif="eth-rt4")
+    switch = tgen.add_switch("s8")
+    switch.add_link(tgen.gears["rt5"], nodeif="eth-rt6")
+    switch.add_link(tgen.gears["rt6"], nodeif="eth-rt5")
 
-        switch = tgen.add_switch("s8")
-        switch.add_link(tgen.gears["rt5"], nodeif="eth-rt6")
-        switch.add_link(tgen.gears["rt6"], nodeif="eth-rt5")
-
-        switch = tgen.add_switch("s9")
-        switch.add_link(tgen.gears["rt6"], nodeif="eth-dst")
-        switch.add_link(tgen.gears["dst"], nodeif="eth-rt6")
+    switch = tgen.add_switch("s9")
+    switch.add_link(tgen.gears["rt6"], nodeif="eth-dst")
+    switch.add_link(tgen.gears["dst"], nodeif="eth-rt6")
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
 
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
 
     frrdir = tgen.config.get(tgen.CONFIG_SECTION, "frrdir")
     if not os.path.isfile(os.path.join(frrdir, "pathd")):
diff --git a/tests/topotests/isis_sr_topo1/test_isis_sr_topo1.py b/tests/topotests/isis_sr_topo1/test_isis_sr_topo1.py
index 8aa187871..a8956bb57 100644
--- a/tests/topotests/isis_sr_topo1/test_isis_sr_topo1.py
+++ b/tests/topotests/isis_sr_topo1/test_isis_sr_topo1.py
@@ -87,59 +87,55 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.isisd]
 
 
-class TemplateTopo(Topo):
-    "Test topology builder"
+def build_topo(tgen):
+    "Build function"
 
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+    #
+    # Define FRR Routers
+    #
+    for router in ["rt1", "rt2", "rt3", "rt4", "rt5", "rt6"]:
+        tgen.add_router(router)
 
-        #
-        # Define FRR Routers
-        #
-        for router in ["rt1", "rt2", "rt3", "rt4", "rt5", "rt6"]:
-            tgen.add_router(router)
+    #
+    # Define connections
+    #
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["rt1"], nodeif="eth-sw1")
+    switch.add_link(tgen.gears["rt2"], nodeif="eth-sw1")
+    switch.add_link(tgen.gears["rt3"], nodeif="eth-sw1")
 
-        #
-        # Define connections
-        #
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["rt1"], nodeif="eth-sw1")
-        switch.add_link(tgen.gears["rt2"], nodeif="eth-sw1")
-        switch.add_link(tgen.gears["rt3"], nodeif="eth-sw1")
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["rt2"], nodeif="eth-rt4-1")
+    switch.add_link(tgen.gears["rt4"], nodeif="eth-rt2-1")
 
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["rt2"], nodeif="eth-rt4-1")
-        switch.add_link(tgen.gears["rt4"], nodeif="eth-rt2-1")
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["rt2"], nodeif="eth-rt4-2")
+    switch.add_link(tgen.gears["rt4"], nodeif="eth-rt2-2")
 
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["rt2"], nodeif="eth-rt4-2")
-        switch.add_link(tgen.gears["rt4"], nodeif="eth-rt2-2")
+    switch = tgen.add_switch("s4")
+    switch.add_link(tgen.gears["rt3"], nodeif="eth-rt5-1")
+    switch.add_link(tgen.gears["rt5"], nodeif="eth-rt3-1")
 
-        switch = tgen.add_switch("s4")
-        switch.add_link(tgen.gears["rt3"], nodeif="eth-rt5-1")
-        switch.add_link(tgen.gears["rt5"], nodeif="eth-rt3-1")
+    switch = tgen.add_switch("s5")
+    switch.add_link(tgen.gears["rt3"], nodeif="eth-rt5-2")
+    switch.add_link(tgen.gears["rt5"], nodeif="eth-rt3-2")
 
-        switch = tgen.add_switch("s5")
-        switch.add_link(tgen.gears["rt3"], nodeif="eth-rt5-2")
-        switch.add_link(tgen.gears["rt5"], nodeif="eth-rt3-2")
+    switch = tgen.add_switch("s6")
+    switch.add_link(tgen.gears["rt4"], nodeif="eth-rt5")
+    switch.add_link(tgen.gears["rt5"], nodeif="eth-rt4")
 
-        switch = tgen.add_switch("s6")
-        switch.add_link(tgen.gears["rt4"], nodeif="eth-rt5")
-        switch.add_link(tgen.gears["rt5"], nodeif="eth-rt4")
+    switch = tgen.add_switch("s7")
+    switch.add_link(tgen.gears["rt4"], nodeif="eth-rt6")
+    switch.add_link(tgen.gears["rt6"], nodeif="eth-rt4")
 
-        switch = tgen.add_switch("s7")
-        switch.add_link(tgen.gears["rt4"], nodeif="eth-rt6")
-        switch.add_link(tgen.gears["rt6"], nodeif="eth-rt4")
-
-        switch = tgen.add_switch("s8")
-        switch.add_link(tgen.gears["rt5"], nodeif="eth-rt6")
-        switch.add_link(tgen.gears["rt6"], nodeif="eth-rt5")
+    switch = tgen.add_switch("s8")
+    switch.add_link(tgen.gears["rt5"], nodeif="eth-rt6")
+    switch.add_link(tgen.gears["rt6"], nodeif="eth-rt5")
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/isis_tilfa_topo1/test_isis_tilfa_topo1.py b/tests/topotests/isis_tilfa_topo1/test_isis_tilfa_topo1.py
index 351bce99e..37ce25312 100755
--- a/tests/topotests/isis_tilfa_topo1/test_isis_tilfa_topo1.py
+++ b/tests/topotests/isis_tilfa_topo1/test_isis_tilfa_topo1.py
@@ -178,7 +178,7 @@ def build_topo(tgen):
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/isis_topo1/test_isis_topo1.py b/tests/topotests/isis_topo1/test_isis_topo1.py
index 29021c562..34bc3830f 100644
--- a/tests/topotests/isis_topo1/test_isis_topo1.py
+++ b/tests/topotests/isis_topo1/test_isis_topo1.py
@@ -61,48 +61,44 @@ VERTEX_TYPE_LIST = [
 ]
 
 
-class ISISTopo1(Topo):
-    "Simple two layer ISIS topology"
-
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
-
-        # Add ISIS routers:
-        # r1      r2
-        #  | sw1  | sw2
-        # r3     r4
-        #  |      |
-        # sw3    sw4
-        #   \    /
-        #     r5
-        for routern in range(1, 6):
-            tgen.add_router("r{}".format(routern))
-
-        # r1 <- sw1 -> r3
-        sw = tgen.add_switch("sw1")
-        sw.add_link(tgen.gears["r1"])
-        sw.add_link(tgen.gears["r3"])
-
-        # r2 <- sw2 -> r4
-        sw = tgen.add_switch("sw2")
-        sw.add_link(tgen.gears["r2"])
-        sw.add_link(tgen.gears["r4"])
-
-        # r3 <- sw3 -> r5
-        sw = tgen.add_switch("sw3")
-        sw.add_link(tgen.gears["r3"])
-        sw.add_link(tgen.gears["r5"])
-
-        # r4 <- sw4 -> r5
-        sw = tgen.add_switch("sw4")
-        sw.add_link(tgen.gears["r4"])
-        sw.add_link(tgen.gears["r5"])
+def build_topo(tgen):
+    "Build function"
+
+    # Add ISIS routers:
+    # r1      r2
+    #  | sw1  | sw2
+    # r3     r4
+    #  |      |
+    # sw3    sw4
+    #   \    /
+    #     r5
+    for routern in range(1, 6):
+        tgen.add_router("r{}".format(routern))
+
+    # r1 <- sw1 -> r3
+    sw = tgen.add_switch("sw1")
+    sw.add_link(tgen.gears["r1"])
+    sw.add_link(tgen.gears["r3"])
+
+    # r2 <- sw2 -> r4
+    sw = tgen.add_switch("sw2")
+    sw.add_link(tgen.gears["r2"])
+    sw.add_link(tgen.gears["r4"])
+
+    # r3 <- sw3 -> r5
+    sw = tgen.add_switch("sw3")
+    sw.add_link(tgen.gears["r3"])
+    sw.add_link(tgen.gears["r5"])
+
+    # r4 <- sw4 -> r5
+    sw = tgen.add_switch("sw4")
+    sw.add_link(tgen.gears["r4"])
+    sw.add_link(tgen.gears["r5"])
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(ISISTopo1, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     # For all registered routers, load the zebra configuration file
diff --git a/tests/topotests/isis_topo1_vrf/test_isis_topo1_vrf.py b/tests/topotests/isis_topo1_vrf/test_isis_topo1_vrf.py
index 9c15ee342..620fc333b 100644
--- a/tests/topotests/isis_topo1_vrf/test_isis_topo1_vrf.py
+++ b/tests/topotests/isis_topo1_vrf/test_isis_topo1_vrf.py
@@ -61,48 +61,44 @@ VERTEX_TYPE_LIST = [
 ]
 
 
-class ISISTopo1(Topo):
-    "Simple two layer ISIS vrf topology"
-
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
-
-        # Add ISIS routers:
-        # r1      r2
-        #  | sw1  | sw2
-        # r3     r4
-        #  |      |
-        # sw3    sw4
-        #   \    /
-        #     r5
-        for routern in range(1, 6):
-            tgen.add_router("r{}".format(routern))
-
-        # r1 <- sw1 -> r3
-        sw = tgen.add_switch("sw1")
-        sw.add_link(tgen.gears["r1"])
-        sw.add_link(tgen.gears["r3"])
-
-        # r2 <- sw2 -> r4
-        sw = tgen.add_switch("sw2")
-        sw.add_link(tgen.gears["r2"])
-        sw.add_link(tgen.gears["r4"])
-
-        # r3 <- sw3 -> r5
-        sw = tgen.add_switch("sw3")
-        sw.add_link(tgen.gears["r3"])
-        sw.add_link(tgen.gears["r5"])
-
-        # r4 <- sw4 -> r5
-        sw = tgen.add_switch("sw4")
-        sw.add_link(tgen.gears["r4"])
-        sw.add_link(tgen.gears["r5"])
+def build_topo(tgen):
+    "Build function"
+
+    # Add ISIS routers:
+    # r1      r2
+    #  | sw1  | sw2
+    # r3     r4
+    #  |      |
+    # sw3    sw4
+    #   \    /
+    #     r5
+    for routern in range(1, 6):
+        tgen.add_router("r{}".format(routern))
+
+    # r1 <- sw1 -> r3
+    sw = tgen.add_switch("sw1")
+    sw.add_link(tgen.gears["r1"])
+    sw.add_link(tgen.gears["r3"])
+
+    # r2 <- sw2 -> r4
+    sw = tgen.add_switch("sw2")
+    sw.add_link(tgen.gears["r2"])
+    sw.add_link(tgen.gears["r4"])
+
+    # r3 <- sw3 -> r5
+    sw = tgen.add_switch("sw3")
+    sw.add_link(tgen.gears["r3"])
+    sw.add_link(tgen.gears["r5"])
+
+    # r4 <- sw4 -> r5
+    sw = tgen.add_switch("sw4")
+    sw.add_link(tgen.gears["r4"])
+    sw.add_link(tgen.gears["r5"])
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(ISISTopo1, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     logger.info("Testing with VRF Lite support")
diff --git a/tests/topotests/ldp_oc_acl_topo1/test_ldp_oc_acl_topo1.py b/tests/topotests/ldp_oc_acl_topo1/test_ldp_oc_acl_topo1.py
index f26c56e54..42ba24f78 100644
--- a/tests/topotests/ldp_oc_acl_topo1/test_ldp_oc_acl_topo1.py
+++ b/tests/topotests/ldp_oc_acl_topo1/test_ldp_oc_acl_topo1.py
@@ -81,39 +81,35 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.ldpd, pytest.mark.ospfd]
 
 
-class TemplateTopo(Topo):
-    "Test topology builder"
+def build_topo(tgen):
+    "Build function"
 
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+    #
+    # Define FRR Routers
+    #
+    for router in ["r1", "r2", "r3", "r4"]:
+        tgen.add_router(router)
 
-        #
-        # Define FRR Routers
-        #
-        for router in ["r1", "r2", "r3", "r4"]:
-            tgen.add_router(router)
+    #
+    # Define connections
+    #
+    switch = tgen.add_switch("s0")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
-        #
-        # Define connections
-        #
-        switch = tgen.add_switch("s0")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
+    switch.add_link(tgen.gears["r4"])
 
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
-        switch.add_link(tgen.gears["r4"])
-
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/ldp_oc_topo1/test_ldp_oc_topo1.py b/tests/topotests/ldp_oc_topo1/test_ldp_oc_topo1.py
index 5208728a9..78e231b60 100644
--- a/tests/topotests/ldp_oc_topo1/test_ldp_oc_topo1.py
+++ b/tests/topotests/ldp_oc_topo1/test_ldp_oc_topo1.py
@@ -81,39 +81,35 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.ldpd, pytest.mark.ospfd]
 
 
-class TemplateTopo(Topo):
-    "Test topology builder"
+def build_topo(tgen):
+    "Build function"
 
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+    #
+    # Define FRR Routers
+    #
+    for router in ["r1", "r2", "r3", "r4"]:
+        tgen.add_router(router)
 
-        #
-        # Define FRR Routers
-        #
-        for router in ["r1", "r2", "r3", "r4"]:
-            tgen.add_router(router)
+    #
+    # Define connections
+    #
+    switch = tgen.add_switch("s0")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
-        #
-        # Define connections
-        #
-        switch = tgen.add_switch("s0")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
+    switch.add_link(tgen.gears["r4"])
 
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
-        switch.add_link(tgen.gears["r4"])
-
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/ldp_snmp/test_ldp_snmp_topo1.py b/tests/topotests/ldp_snmp/test_ldp_snmp_topo1.py
index f0473257c..a616335d7 100644
--- a/tests/topotests/ldp_snmp/test_ldp_snmp_topo1.py
+++ b/tests/topotests/ldp_snmp/test_ldp_snmp_topo1.py
@@ -83,50 +83,46 @@ from lib.micronet_compat import Topo
 
 pytestmark = [pytest.mark.ldpd, pytest.mark.isisd, pytest.mark.snmp]
 
-class TemplateTopo(Topo):
-    "Test topology builder"
+def build_topo(tgen):
+    "Build function"
 
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+    #
+    # Define FRR Routers
+    #
+    for router in ["ce1", "ce2", "ce3", "r1", "r2", "r3"]:
+        tgen.add_router(router)
 
-        #
-        # Define FRR Routers
-        #
-        for router in ["ce1", "ce2", "ce3", "r1", "r2", "r3"]:
-            tgen.add_router(router)
+    #
+    # Define connections
+    #
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["ce1"])
+    switch.add_link(tgen.gears["r1"])
 
-        #
-        # Define connections
-        #
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["ce1"])
-        switch.add_link(tgen.gears["r1"])
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["ce2"])
+    switch.add_link(tgen.gears["r2"])
 
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["ce2"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["ce3"])
+    switch.add_link(tgen.gears["r3"])
 
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["ce3"])
-        switch.add_link(tgen.gears["r3"])
+    switch = tgen.add_switch("s4")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
-        switch = tgen.add_switch("s4")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s5")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r3"])
 
-        switch = tgen.add_switch("s5")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r3"])
-
-        switch = tgen.add_switch("s6")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
+    switch = tgen.add_switch("s6")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/ldp_sync_isis_topo1/test_ldp_sync_isis_topo1.py b/tests/topotests/ldp_sync_isis_topo1/test_ldp_sync_isis_topo1.py
index 3c26bd5ba..37275ed9e 100644
--- a/tests/topotests/ldp_sync_isis_topo1/test_ldp_sync_isis_topo1.py
+++ b/tests/topotests/ldp_sync_isis_topo1/test_ldp_sync_isis_topo1.py
@@ -83,50 +83,46 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.isisd, pytest.mark.ldpd]
 
 
-class TemplateTopo(Topo):
-    "Test topology builder"
+def build_topo(tgen):
+    "Build function"
 
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+    #
+    # Define FRR Routers
+    #
+    for router in ["ce1", "ce2", "ce3", "r1", "r2", "r3"]:
+        tgen.add_router(router)
 
-        #
-        # Define FRR Routers
-        #
-        for router in ["ce1", "ce2", "ce3", "r1", "r2", "r3"]:
-            tgen.add_router(router)
+    #
+    # Define connections
+    #
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["ce1"])
+    switch.add_link(tgen.gears["r1"])
 
-        #
-        # Define connections
-        #
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["ce1"])
-        switch.add_link(tgen.gears["r1"])
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["ce2"])
+    switch.add_link(tgen.gears["r2"])
 
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["ce2"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["ce3"])
+    switch.add_link(tgen.gears["r3"])
 
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["ce3"])
-        switch.add_link(tgen.gears["r3"])
+    switch = tgen.add_switch("s4")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
-        switch = tgen.add_switch("s4")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s5")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r3"])
 
-        switch = tgen.add_switch("s5")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r3"])
-
-        switch = tgen.add_switch("s6")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
+    switch = tgen.add_switch("s6")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/ldp_sync_ospf_topo1/test_ldp_sync_ospf_topo1.py b/tests/topotests/ldp_sync_ospf_topo1/test_ldp_sync_ospf_topo1.py
index c5bd97edf..5412fa600 100644
--- a/tests/topotests/ldp_sync_ospf_topo1/test_ldp_sync_ospf_topo1.py
+++ b/tests/topotests/ldp_sync_ospf_topo1/test_ldp_sync_ospf_topo1.py
@@ -82,50 +82,46 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.ldpd, pytest.mark.ospfd]
 
 
-class TemplateTopo(Topo):
-    "Test topology builder"
+def build_topo(tgen):
+    "Build function"
 
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+    #
+    # Define FRR Routers
+    #
+    for router in ["ce1", "ce2", "ce3", "r1", "r2", "r3"]:
+        tgen.add_router(router)
 
-        #
-        # Define FRR Routers
-        #
-        for router in ["ce1", "ce2", "ce3", "r1", "r2", "r3"]:
-            tgen.add_router(router)
+    #
+    # Define connections
+    #
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["ce1"])
+    switch.add_link(tgen.gears["r1"])
 
-        #
-        # Define connections
-        #
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["ce1"])
-        switch.add_link(tgen.gears["r1"])
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["ce2"])
+    switch.add_link(tgen.gears["r2"])
 
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["ce2"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["ce3"])
+    switch.add_link(tgen.gears["r3"])
 
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["ce3"])
-        switch.add_link(tgen.gears["r3"])
+    switch = tgen.add_switch("s4")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
-        switch = tgen.add_switch("s4")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s5")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r3"])
 
-        switch = tgen.add_switch("s5")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r3"])
-
-        switch = tgen.add_switch("s6")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
+    switch = tgen.add_switch("s6")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/ldp_topo1/test_ldp_topo1.py b/tests/topotests/ldp_topo1/test_ldp_topo1.py
index 62b763ce7..f6d28b66a 100644
--- a/tests/topotests/ldp_topo1/test_ldp_topo1.py
+++ b/tests/topotests/ldp_topo1/test_ldp_topo1.py
@@ -68,7 +68,7 @@ from time import sleep
 sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 from lib import topotest
 from lib.micronet_compat import Topo
-from lib.micronet_compat import Mininet
+from lib.topogen import Topogen, get_topogen
 
 fatal_error = ""
 
@@ -81,73 +81,25 @@ pytestmark = [pytest.mark.ldpd, pytest.mark.ospfd]
 #####################################################
 
 
-class NetworkTopo(Topo):
-    "LDP Test Topology 1"
+def build_topo(tgen):
 
-    def build(self, **_opts):
-
-        # Setup Routers
-        router = {}
-        for i in range(1, 5):
-            router[i] = topotest.addRouter(self, "r%s" % i)
-
-        # Setup Switches, add Interfaces and Connections
-        switch = {}
-        # First switch
-        switch[0] = self.addSwitch("sw0")
-        self.addLink(
-            switch[0],
-            router[1],
-            intfName2="r1-eth0",
-            addr1="80:AA:00:00:00:00",
-            addr2="00:11:00:01:00:00",
-        )
-        self.addLink(
-            switch[0],
-            router[2],
-            intfName2="r2-eth0",
-            addr1="80:AA:00:00:00:01",
-            addr2="00:11:00:02:00:00",
-        )
-        # Second switch
-        switch[1] = self.addSwitch("sw1")
-        self.addLink(
-            switch[1],
-            router[2],
-            intfName2="r2-eth1",
-            addr1="80:AA:00:01:00:00",
-            addr2="00:11:00:02:00:01",
-        )
-        self.addLink(
-            switch[1],
-            router[3],
-            intfName2="r3-eth0",
-            addr1="80:AA:00:01:00:01",
-            addr2="00:11:00:03:00:00",
-        )
-        self.addLink(
-            switch[1],
-            router[4],
-            intfName2="r4-eth0",
-            addr1="80:AA:00:01:00:02",
-            addr2="00:11:00:04:00:00",
-        )
-        # Third switch
-        switch[2] = self.addSwitch("sw2")
-        self.addLink(
-            switch[2],
-            router[2],
-            intfName2="r2-eth2",
-            addr1="80:AA:00:02:00:00",
-            addr2="00:11:00:02:00:02",
-        )
-        self.addLink(
-            switch[2],
-            router[3],
-            intfName2="r3-eth1",
-            addr1="80:AA:00:02:00:01",
-            addr2="00:11:00:03:00:01",
-        )
+    # Setup Routers
+    for i in range(1, 5):
+        tgen.add_router("r%s" % i)
+
+    # First switch
+    switch = tgen.add_switch("sw0")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
+    # Second switch
+    switch = tgen.add_switch("sw1")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
+    switch.add_link(tgen.gears["r4"])
+    # Third switch
+    switch = tgen.add_switch("sw2")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
 
 
 #####################################################
@@ -158,48 +110,36 @@ class NetworkTopo(Topo):
 
 
 def setup_module(module):
-    global topo, net
-    global fatal_error
-
     print("\n\n** %s: Setup Topology" % module.__name__)
     print("******************************************\n")
 
-    print("Cleanup old Mininet runs")
-    os.system("sudo mn -c > /dev/null 2>&1")
-
     thisDir = os.path.dirname(os.path.realpath(__file__))
-    topo = NetworkTopo()
+    tgen = Topogen(build_topo, module.__name__)
+    tgen.start_topology()
 
-    net = Mininet(controller=None, topo=topo)
-    net.start()
+    net = tgen.net
 
     # Starting Routers
     for i in range(1, 5):
         net["r%s" % i].loadConf("zebra", "%s/r%s/zebra.conf" % (thisDir, i))
         net["r%s" % i].loadConf("ospfd", "%s/r%s/ospfd.conf" % (thisDir, i))
         net["r%s" % i].loadConf("ldpd", "%s/r%s/ldpd.conf" % (thisDir, i))
-        fatal_error = net["r%s" % i].startRouter()
-
-        if fatal_error != "":
-            break
+        tgen.gears["r%s" % i].start()
 
     # For debugging after starting FRR daemons, uncomment the next line
     # CLI(net)
 
 
 def teardown_module(module):
-    global net
-
     print("\n\n** %s: Shutdown Topology" % module.__name__)
     print("******************************************\n")
-
-    # End - Shutdown network
-    net.stop()
+    tgen = get_topogen()
+    tgen.stop_topology()
 
 
 def test_router_running():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -220,7 +160,7 @@ def test_router_running():
 
 def test_mpls_interfaces():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -286,7 +226,7 @@ def test_mpls_interfaces():
 
 def test_mpls_ldp_neighbor_establish():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -354,7 +294,7 @@ def test_mpls_ldp_neighbor_establish():
 
 def test_mpls_ldp_discovery():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -423,7 +363,7 @@ def test_mpls_ldp_discovery():
 
 def test_mpls_ldp_neighbor():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -493,7 +433,7 @@ def test_mpls_ldp_neighbor():
 
 def test_mpls_ldp_binding():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip this test for now until proper sorting of the output
     # is implemented
@@ -585,7 +525,7 @@ def test_mpls_ldp_binding():
 
 def test_zebra_ipv4_routingTable():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -662,7 +602,7 @@ def test_zebra_ipv4_routingTable():
 
 def test_mpls_table():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -741,7 +681,7 @@ def test_mpls_table():
 
 def test_linux_mpls_routes():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -825,7 +765,7 @@ def test_linux_mpls_routes():
 
 def test_shutdown_check_stderr():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -857,7 +797,7 @@ def test_shutdown_check_stderr():
 
 def test_shutdown_check_memleak():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
diff --git a/tests/topotests/ldp_vpls_topo1/test_ldp_vpls_topo1.py b/tests/topotests/ldp_vpls_topo1/test_ldp_vpls_topo1.py
index 8dc8039c9..c77c96b17 100644
--- a/tests/topotests/ldp_vpls_topo1/test_ldp_vpls_topo1.py
+++ b/tests/topotests/ldp_vpls_topo1/test_ldp_vpls_topo1.py
@@ -83,50 +83,46 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.ldpd, pytest.mark.ospfd]
 
 
-class TemplateTopo(Topo):
-    "Test topology builder"
+def build_topo(tgen):
+    "Build function"
 
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+    #
+    # Define FRR Routers
+    #
+    for router in ["ce1", "ce2", "ce3", "r1", "r2", "r3"]:
+        tgen.add_router(router)
 
-        #
-        # Define FRR Routers
-        #
-        for router in ["ce1", "ce2", "ce3", "r1", "r2", "r3"]:
-            tgen.add_router(router)
+    #
+    # Define connections
+    #
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["ce1"])
+    switch.add_link(tgen.gears["r1"])
 
-        #
-        # Define connections
-        #
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["ce1"])
-        switch.add_link(tgen.gears["r1"])
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["ce2"])
+    switch.add_link(tgen.gears["r2"])
 
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["ce2"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["ce3"])
+    switch.add_link(tgen.gears["r3"])
 
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["ce3"])
-        switch.add_link(tgen.gears["r3"])
+    switch = tgen.add_switch("s4")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
-        switch = tgen.add_switch("s4")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s5")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r3"])
 
-        switch = tgen.add_switch("s5")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r3"])
-
-        switch = tgen.add_switch("s6")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
+    switch = tgen.add_switch("s6")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/lib/ltemplate.py b/tests/topotests/lib/ltemplate.py
index 1ea033a12..ef2eb8cab 100644
--- a/tests/topotests/lib/ltemplate.py
+++ b/tests/topotests/lib/ltemplate.py
@@ -72,7 +72,7 @@ class LTemplate:
     def setup_module(self, mod):
         "Sets up the pytest environment"
         # This function initiates the topology build with Topogen...
-        tgen = Topogen(customize.ThisTestTopo, mod.__name__)
+        tgen = Topogen(customize.build_topo, mod.__name__)
         # ... and here it calls Mininet initialization functions.
         tgen.start_topology()
 
diff --git a/tests/topotests/msdp_mesh_topo1/test_msdp_mesh_topo1.py b/tests/topotests/msdp_mesh_topo1/test_msdp_mesh_topo1.py
index a10477d28..121f4a7fd 100644
--- a/tests/topotests/msdp_mesh_topo1/test_msdp_mesh_topo1.py
+++ b/tests/topotests/msdp_mesh_topo1/test_msdp_mesh_topo1.py
@@ -113,40 +113,36 @@ def close_applications():
         p.wait()
 
 
-class MSDPMeshTopo1(Topo):
-    "Test topology builder"
+def build_topo(tgen):
+    "Build function"
 
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+    # Create 3 routers
+    for routern in range(1, 4):
+        tgen.add_router("r{}".format(routern))
 
-        # Create 3 routers
-        for routern in range(1, 4):
-            tgen.add_router("r{}".format(routern))
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
 
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
+    # Create stub networks for multicast traffic.
+    tgen.add_host("h1", "192.168.10.2/24", "via 192.168.10.1")
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["h1"])
 
-        # Create stub networks for multicast traffic.
-        tgen.add_host("h1", "192.168.10.2/24", "via 192.168.10.1")
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["h1"])
-
-        tgen.add_host("h2", "192.168.30.2/24", "via 192.168.30.1")
-        switch = tgen.add_switch("s4")
-        switch.add_link(tgen.gears["r3"])
-        switch.add_link(tgen.gears["h2"])
+    tgen.add_host("h2", "192.168.30.2/24", "via 192.168.30.1")
+    switch = tgen.add_switch("s4")
+    switch.add_link(tgen.gears["r3"])
+    switch.add_link(tgen.gears["h2"])
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(MSDPMeshTopo1, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/msdp_topo1/test_msdp_topo1.py b/tests/topotests/msdp_topo1/test_msdp_topo1.py
index 796706a2e..8fad62db7 100755
--- a/tests/topotests/msdp_topo1/test_msdp_topo1.py
+++ b/tests/topotests/msdp_topo1/test_msdp_topo1.py
@@ -113,50 +113,46 @@ def close_applications():
         app_clients[host]["fd"].close()
 
 
-class MSDPTopo1(Topo):
-    "Test topology builder"
+def build_topo(tgen):
+    "Build function"
 
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+    # Create 4 routers
+    for routern in range(1, 5):
+        tgen.add_router("r{}".format(routern))
 
-        # Create 4 routers
-        for routern in range(1, 5):
-            tgen.add_router("r{}".format(routern))
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r3"])
 
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r3"])
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r4"])
 
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r4"])
+    switch = tgen.add_switch("s4")
+    # switch.add_link(tgen.gears["r3"])
+    switch.add_link(tgen.gears["r4"])
 
-        switch = tgen.add_switch("s4")
-        #switch.add_link(tgen.gears["r3"])
-        switch.add_link(tgen.gears["r4"])
+    switch = tgen.add_switch("s5")
+    switch.add_link(tgen.gears["r4"])
 
-        switch = tgen.add_switch("s5")
-        switch.add_link(tgen.gears["r4"])
+    # Create a host connected and direct at r4:
+    tgen.add_host("h1", "192.168.4.100/24", "via 192.168.4.1")
+    switch.add_link(tgen.gears["h1"])
 
-        # Create a host connected and direct at r4:
-        tgen.add_host("h1", "192.168.4.100/24", "via 192.168.4.1")
-        switch.add_link(tgen.gears["h1"])
-
-        # Create a host connected and direct at r1:
-        switch = tgen.add_switch("s6")
-        tgen.add_host("h2", "192.168.10.100/24", "via 192.168.10.1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["h2"])
+    # Create a host connected and direct at r1:
+    switch = tgen.add_switch("s6")
+    tgen.add_host("h2", "192.168.10.100/24", "via 192.168.10.1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["h2"])
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(MSDPTopo1, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/multicast_pim_bsm_topo1/test_mcast_pim_bsmp_01.py b/tests/topotests/multicast_pim_bsm_topo1/test_mcast_pim_bsmp_01.py
index 5cd5cd155..df1cce654 100644
--- a/tests/topotests/multicast_pim_bsm_topo1/test_mcast_pim_bsmp_01.py
+++ b/tests/topotests/multicast_pim_bsm_topo1/test_mcast_pim_bsmp_01.py
@@ -113,16 +113,8 @@ from lib.pim import (
 from lib.topolog import logger
 from lib.topojson import build_topo_from_json, build_config_from_json
 
-pytestmark = [pytest.mark.pimd, pytest.mark.staticd]
-
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/mcast_pim_bsmp_01.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
+pytestmark = [pytest.mark.pimd, pytest.mark.staticd]
 
 TOPOLOGY = """
 
@@ -151,21 +143,6 @@ BSR1_ADDR = "1.1.2.7/32"
 BSR2_ADDR = "10.2.1.1/32"
 
 
-class CreateTopo(Topo):
-    """
-    Test BasicTopo - topology 1
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function"""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
@@ -186,7 +163,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/mcast_pim_bsmp_01.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # get list of daemons needs to be started for this suite.
diff --git a/tests/topotests/multicast_pim_bsm_topo2/test_mcast_pim_bsmp_02.py b/tests/topotests/multicast_pim_bsm_topo2/test_mcast_pim_bsmp_02.py
index 115d0bff0..64c284f7f 100644
--- a/tests/topotests/multicast_pim_bsm_topo2/test_mcast_pim_bsmp_02.py
+++ b/tests/topotests/multicast_pim_bsm_topo2/test_mcast_pim_bsmp_02.py
@@ -107,13 +107,6 @@ from lib.topojson import build_topo_from_json, build_config_from_json
 pytestmark = [pytest.mark.pimd, pytest.mark.staticd]
 
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/mcast_pim_bsmp_02.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 
 TOPOLOGY = """
 
@@ -142,21 +135,6 @@ BSR1_ADDR = "1.1.2.7/32"
 BSR2_ADDR = "10.2.1.1/32"
 
 
-class CreateTopo(Topo):
-    """
-    Test BasicTopo - topology 1
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function"""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
@@ -177,7 +155,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/mcast_pim_bsmp_02.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # get list of daemons needs to be started for this suite.
diff --git a/tests/topotests/multicast_pim_sm_topo1/test_multicast_pim_sm_topo1.py b/tests/topotests/multicast_pim_sm_topo1/test_multicast_pim_sm_topo1.py
index d808a60c0..9eb3d8cc5 100755
--- a/tests/topotests/multicast_pim_sm_topo1/test_multicast_pim_sm_topo1.py
+++ b/tests/topotests/multicast_pim_sm_topo1/test_multicast_pim_sm_topo1.py
@@ -108,16 +108,8 @@ from lib.pim import (
 from lib.topolog import logger
 from lib.topojson import build_topo_from_json, build_config_from_json
 
-pytestmark = [pytest.mark.pimd]
-
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/multicast_pim_sm_topo1.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
+pytestmark = [pytest.mark.pimd]
 
 TOPOLOGY = """
 
@@ -170,21 +162,6 @@ GROUP_RANGE_3 = [
 IGMP_JOIN_RANGE_3 = ["227.1.1.1", "227.1.1.2", "227.1.1.3", "227.1.1.4", "227.1.1.5"]
 
 
-class CreateTopo(Topo):
-    """
-    Test BasicTopo - topology 1
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function"""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
@@ -204,11 +181,15 @@ def setup_module(mod):
 
     logger.info("Running setup_module to create topology")
 
-    tgen = Topogen(CreateTopo, mod.__name__)
+    testdir = os.path.dirname(os.path.realpath(__file__))
+    json_file = "{}/multicast_pim_sm_topo1.json".format(testdir)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # get list of daemons needs to be started for this suite.
-    daemons = topo_daemons(tgen, topo)
+    daemons = topo_daemons(tgen, tgen.json_topo)
 
     # Starting topology, create tmp files which are loaded to routers
     #  to start deamons and then start routers
diff --git a/tests/topotests/multicast_pim_sm_topo2/test_multicast_pim_sm_topo2.py b/tests/topotests/multicast_pim_sm_topo2/test_multicast_pim_sm_topo2.py
index 0b6894220..96886b0d9 100755
--- a/tests/topotests/multicast_pim_sm_topo2/test_multicast_pim_sm_topo2.py
+++ b/tests/topotests/multicast_pim_sm_topo2/test_multicast_pim_sm_topo2.py
@@ -102,16 +102,8 @@ from lib.pim import (
 from lib.topolog import logger
 from lib.topojson import build_topo_from_json, build_config_from_json
 
-pytestmark = [pytest.mark.pimd]
-
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/multicast_pim_sm_topo2.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
+pytestmark = [pytest.mark.pimd]
 
 TOPOLOGY = """
 
@@ -164,21 +156,6 @@ GROUP_RANGE_3 = [
 IGMP_JOIN_RANGE_3 = ["227.1.1.1", "227.1.1.2", "227.1.1.3", "227.1.1.4", "227.1.1.5"]
 
 
-class CreateTopo(Topo):
-    """
-    Test BasicTopo - topology 1
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function"""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
@@ -198,7 +175,10 @@ def setup_module(mod):
 
     logger.info("Running setup_module to create topology")
 
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/multicast_pim_sm_topo2.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # get list of daemons needs to be started for this suite.
diff --git a/tests/topotests/multicast_pim_sm_topo3/test_multicast_pim_sm_topo3.py b/tests/topotests/multicast_pim_sm_topo3/test_multicast_pim_sm_topo3.py
index f3688e2f5..7c04dba06 100755
--- a/tests/topotests/multicast_pim_sm_topo3/test_multicast_pim_sm_topo3.py
+++ b/tests/topotests/multicast_pim_sm_topo3/test_multicast_pim_sm_topo3.py
@@ -88,7 +88,6 @@ from lib.common_config import (
     add_interfaces_to_vlan,
     tcpdump_capture_start,
     tcpdump_capture_stop,
-    LOGDIR,
     check_router_status,
     required_linux_kernel_version,
     topo_daemons,
@@ -114,13 +113,8 @@ from lib.pim import (
 from lib.topolog import logger
 from lib.topojson import build_topo_from_json, build_config_from_json
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/multicast_pim_sm_topo3.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
+CWD = os.path.dirname(os.path.realpath(__file__))
+pytestmark = pytest.mark.pimd
 
 TOPOLOGY = """
 
@@ -179,21 +173,6 @@ SAME_VLAN_IP_3 = {"ip": "10.1.1.3", "subnet": "255.255.255.0", "cidr": "24"}
 SAME_VLAN_IP_4 = {"ip": "10.1.1.4", "subnet": "255.255.255.0", "cidr": "24"}
 
 
-class CreateTopo(Topo):
-    """
-    Test BasicTopo - topology 1
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function"""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
@@ -213,7 +192,10 @@ def setup_module(mod):
 
     logger.info("Running setup_module to create topology")
 
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/multicast_pim_sm_topo3.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # get list of daemons needs to be started for this suite.
diff --git a/tests/topotests/multicast_pim_sm_topo3/test_multicast_pim_sm_topo4.py b/tests/topotests/multicast_pim_sm_topo3/test_multicast_pim_sm_topo4.py
index d2bddc43b..445dab837 100755
--- a/tests/topotests/multicast_pim_sm_topo3/test_multicast_pim_sm_topo4.py
+++ b/tests/topotests/multicast_pim_sm_topo3/test_multicast_pim_sm_topo4.py
@@ -101,14 +101,6 @@ from lib.pim import (
 from lib.topolog import logger
 from lib.topojson import build_topo_from_json, build_config_from_json
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/multicast_pim_sm_topo4.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
-
 TOPOLOGY = """
 
 
@@ -149,21 +141,6 @@ NEW_ADDRESS_1_SUBNET = "192.168.20.1/24"
 NEW_ADDRESS_2_SUBNET = "192.168.20.2/24"
 
 
-class CreateTopo(Topo):
-    """
-    Test BasicTopo - topology 1
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function"""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
@@ -183,7 +160,10 @@ def setup_module(mod):
 
     logger.info("Running setup_module to create topology")
 
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/multicast_pim_sm_topo4.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # get list of daemons needs to be started for this suite.
diff --git a/tests/topotests/multicast_pim_static_rp_topo1/test_multicast_pim_static_rp.py b/tests/topotests/multicast_pim_static_rp_topo1/test_multicast_pim_static_rp.py
index b57c5b16d..b1ffd3786 100755
--- a/tests/topotests/multicast_pim_static_rp_topo1/test_multicast_pim_static_rp.py
+++ b/tests/topotests/multicast_pim_static_rp_topo1/test_multicast_pim_static_rp.py
@@ -187,23 +187,11 @@ SOURCE_ADDRESS = "10.0.6.2"
 SOURCE = "Static"
 
 
-class CreateTopo(Topo):
-    """
-    Test BasicTopo - topology 1
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function"""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, TOPO)
+def build_topo(tgen):
+    """Build function"""
 
-    def dumdum(self):
-        """ Dummy """
-        print("%s", self.name)
+    # Building topology from json file
+    build_topo_from_json(tgen, TOPO)
 
 
 def setup_module(mod):
diff --git a/tests/topotests/nhrp_topo/test_nhrp_topo.py b/tests/topotests/nhrp_topo/test_nhrp_topo.py
index 6d3cc3a55..19be9a8ff 100644
--- a/tests/topotests/nhrp_topo/test_nhrp_topo.py
+++ b/tests/topotests/nhrp_topo/test_nhrp_topo.py
@@ -48,26 +48,23 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.nhrpd]
 
 
-class NHRPTopo(Topo):
-    "Test topology builder"
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
-
-        # Create 3 routers.
-        for routern in range(1, 4):
-            tgen.add_router('r{}'.format(routern))
-
-        switch = tgen.add_switch('s1')
-        switch.add_link(tgen.gears['r1'])
-        switch.add_link(tgen.gears['r3'])
-        switch = tgen.add_switch('s2')
-        switch.add_link(tgen.gears['r2'])
-        switch.add_link(tgen.gears['r3'])
-        switch = tgen.add_switch('s3')
-        switch.add_link(tgen.gears['r2'])
-        switch = tgen.add_switch('s4')
-        switch.add_link(tgen.gears['r1'])
+def build_topo(tgen):
+    "Build function"
+
+    # Create 3 routers.
+    for routern in range(1, 4):
+        tgen.add_router('r{}'.format(routern))
+
+    switch = tgen.add_switch('s1')
+    switch.add_link(tgen.gears['r1'])
+    switch.add_link(tgen.gears['r3'])
+    switch = tgen.add_switch('s2')
+    switch.add_link(tgen.gears['r2'])
+    switch.add_link(tgen.gears['r3'])
+    switch = tgen.add_switch('s3')
+    switch.add_link(tgen.gears['r2'])
+    switch = tgen.add_switch('s4')
+    switch.add_link(tgen.gears['r1'])
 
 
 def _populate_iface():
@@ -99,7 +96,7 @@ def _populate_iface():
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(NHRPTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/ospf6_topo1/test_ospf6_topo1.py b/tests/topotests/ospf6_topo1/test_ospf6_topo1.py
index 4a4ae3d5b..1bc994aaa 100644
--- a/tests/topotests/ospf6_topo1/test_ospf6_topo1.py
+++ b/tests/topotests/ospf6_topo1/test_ospf6_topo1.py
@@ -91,59 +91,46 @@ from lib.topogen import Topogen, TopoRouter, get_topogen
 from lib.topolog import logger
 import platform
 
-pytestmark = [pytest.mark.ospfd]
-
-
-#####################################################
-##
-##   Network Topology Definition
-##
-#####################################################
-
 
-class NetworkTopo(Topo):
-    "OSPFv3 (IPv6) Test Topology 1"
-
-    def build(self, **_opts):
-        "Build function"
+pytestmark = [pytest.mark.ospfd]
 
-        tgen = get_topogen(self)
 
-        # Create 4 routers
-        for routern in range(1, 5):
-            tgen.add_router("r{}".format(routern))
+def build_topo(tgen):
+    # Create 4 routers
+    for routern in range(1, 5):
+        tgen.add_router("r{}".format(routern))
 
-        #
-        # Wire up the switches and routers
-        # Note that we specify the link names so we match the config files
-        #
+    #
+    # Wire up the switches and routers
+    # Note that we specify the link names so we match the config files
+    #
 
-        # Create a empty network for router 1
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"], nodeif="r1-stubnet")
+    # Create a empty network for router 1
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"], nodeif="r1-stubnet")
 
-        # Create a empty network for router 2
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["r2"], nodeif="r2-stubnet")
+    # Create a empty network for router 2
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r2"], nodeif="r2-stubnet")
 
-        # Create a empty network for router 3
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["r3"], nodeif="r3-stubnet")
+    # Create a empty network for router 3
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["r3"], nodeif="r3-stubnet")
 
-        # Create a empty network for router 4
-        switch = tgen.add_switch("s4")
-        switch.add_link(tgen.gears["r4"], nodeif="r4-stubnet")
+    # Create a empty network for router 4
+    switch = tgen.add_switch("s4")
+    switch.add_link(tgen.gears["r4"], nodeif="r4-stubnet")
 
-        # Interconnect routers 1, 2, and 3
-        switch = tgen.add_switch("s5")
-        switch.add_link(tgen.gears["r1"], nodeif="r1-sw5")
-        switch.add_link(tgen.gears["r2"], nodeif="r2-sw5")
-        switch.add_link(tgen.gears["r3"], nodeif="r3-sw5")
+    # Interconnect routers 1, 2, and 3
+    switch = tgen.add_switch("s5")
+    switch.add_link(tgen.gears["r1"], nodeif="r1-sw5")
+    switch.add_link(tgen.gears["r2"], nodeif="r2-sw5")
+    switch.add_link(tgen.gears["r3"], nodeif="r3-sw5")
 
-        # Interconnect routers 3 and 4
-        switch = tgen.add_switch("s6")
-        switch.add_link(tgen.gears["r3"], nodeif="r3-sw6")
-        switch.add_link(tgen.gears["r4"], nodeif="r4-sw6")
+    # Interconnect routers 3 and 4
+    switch = tgen.add_switch("s6")
+    switch.add_link(tgen.gears["r3"], nodeif="r3-sw6")
+    switch.add_link(tgen.gears["r4"], nodeif="r4-sw6")
 
 
 #####################################################
@@ -156,7 +143,7 @@ class NetworkTopo(Topo):
 def setup_module(mod):
     "Sets up the pytest environment"
 
-    tgen = Topogen(NetworkTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     logger.info("** %s: Setup Topology" % mod.__name__)
diff --git a/tests/topotests/ospf6_topo1_vrf/test_ospf6_topo1_vrf.py b/tests/topotests/ospf6_topo1_vrf/test_ospf6_topo1_vrf.py
index 28e89dfa5..174cecfef 100755
--- a/tests/topotests/ospf6_topo1_vrf/test_ospf6_topo1_vrf.py
+++ b/tests/topotests/ospf6_topo1_vrf/test_ospf6_topo1_vrf.py
@@ -94,59 +94,49 @@ from lib.topolog import logger
 from lib.topotest import iproute2_is_vrf_capable
 from lib.common_config import required_linux_kernel_version
 
-pytestmark = [pytest.mark.ospfd]
-
-
-#####################################################
-##
-##   Network Topology Definition
-##
-#####################################################
 
+pytestmark = [pytest.mark.ospfd]
 
-class NetworkTopo(Topo):
-    "OSPFv3 (IPv6) Test Topology 1"
 
-    def build(self, **_opts):
-        "Build function"
+def build_topo(tgen):
+    "Build function"
 
-        tgen = get_topogen(self)
 
-        # Create 4 routers
-        for routern in range(1, 5):
-            tgen.add_router("r{}".format(routern))
+    # Create 4 routers
+    for routern in range(1, 5):
+        tgen.add_router("r{}".format(routern))
 
-        #
-        # Wire up the switches and routers
-        # Note that we specify the link names so we match the config files
-        #
+    #
+    # Wire up the switches and routers
+    # Note that we specify the link names so we match the config files
+    #
 
-        # Create a empty network for router 1
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"], nodeif="r1-stubnet")
+    # Create a empty network for router 1
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"], nodeif="r1-stubnet")
 
-        # Create a empty network for router 2
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["r2"], nodeif="r2-stubnet")
+    # Create a empty network for router 2
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r2"], nodeif="r2-stubnet")
 
-        # Create a empty network for router 3
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["r3"], nodeif="r3-stubnet")
+    # Create a empty network for router 3
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["r3"], nodeif="r3-stubnet")
 
-        # Create a empty network for router 4
-        switch = tgen.add_switch("s4")
-        switch.add_link(tgen.gears["r4"], nodeif="r4-stubnet")
+    # Create a empty network for router 4
+    switch = tgen.add_switch("s4")
+    switch.add_link(tgen.gears["r4"], nodeif="r4-stubnet")
 
-        # Interconnect routers 1, 2, and 3
-        switch = tgen.add_switch("s5")
-        switch.add_link(tgen.gears["r1"], nodeif="r1-sw5")
-        switch.add_link(tgen.gears["r2"], nodeif="r2-sw5")
-        switch.add_link(tgen.gears["r3"], nodeif="r3-sw5")
+    # Interconnect routers 1, 2, and 3
+    switch = tgen.add_switch("s5")
+    switch.add_link(tgen.gears["r1"], nodeif="r1-sw5")
+    switch.add_link(tgen.gears["r2"], nodeif="r2-sw5")
+    switch.add_link(tgen.gears["r3"], nodeif="r3-sw5")
 
-        # Interconnect routers 3 and 4
-        switch = tgen.add_switch("s6")
-        switch.add_link(tgen.gears["r3"], nodeif="r3-sw6")
-        switch.add_link(tgen.gears["r4"], nodeif="r4-sw6")
+    # Interconnect routers 3 and 4
+    switch = tgen.add_switch("s6")
+    switch.add_link(tgen.gears["r3"], nodeif="r3-sw6")
+    switch.add_link(tgen.gears["r4"], nodeif="r4-sw6")
 
 
 #####################################################
@@ -164,7 +154,7 @@ def setup_module(mod):
     if result is not True:
         pytest.skip("Kernel requirements are not met")
 
-    tgen = Topogen(NetworkTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     logger.info("** %s: Setup Topology" % mod.__name__)
diff --git a/tests/topotests/ospf6_topo2/test_ospf6_topo2.py b/tests/topotests/ospf6_topo2/test_ospf6_topo2.py
index e64000b07..c1ff243fd 100644
--- a/tests/topotests/ospf6_topo2/test_ospf6_topo2.py
+++ b/tests/topotests/ospf6_topo2/test_ospf6_topo2.py
@@ -95,33 +95,29 @@ def expect_ospfv3_routes(router, routes, wait=5, detail=False):
     assert result is None, assertmsg
 
 
-class OSPFv3Topo2(Topo):
-    "Test topology builder"
+def build_topo(tgen):
+    "Build function"
 
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+    # Create 4 routers
+    for routern in range(1, 5):
+        tgen.add_router("r{}".format(routern))
 
-        # Create 4 routers
-        for routern in range(1, 5):
-            tgen.add_router("r{}".format(routern))
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
 
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
-
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r4"])
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r4"])
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(OSPFv3Topo2, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/ospf_basic_functionality/test_ospf_asbr_summary_topo1.py b/tests/topotests/ospf_basic_functionality/test_ospf_asbr_summary_topo1.py
index 392cca3a1..dfcbf7bcb 100644
--- a/tests/topotests/ospf_basic_functionality/test_ospf_asbr_summary_topo1.py
+++ b/tests/topotests/ospf_basic_functionality/test_ospf_asbr_summary_topo1.py
@@ -75,13 +75,6 @@ pytestmark = [pytest.mark.ospfd, pytest.mark.staticd]
 
 # Global variables
 topo = None
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/ospf_asbr_summary_topo1.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 
 NETWORK = {
     "ipv4": [
@@ -132,28 +125,12 @@ TESTCASES =
 """
 
 
-class CreateTopo(Topo):
-    """
-    Test topology builder.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
 
     * `mod`: module name
     """
-    global topo
     testsuite_run_time = time.asctime(time.localtime(time.time()))
     logger.info("Testsuite start time: {}".format(testsuite_run_time))
     logger.info("=" * 40)
@@ -161,7 +138,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/ospf_asbr_summary_topo1.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # get list of daemons needs to be started for this suite.
diff --git a/tests/topotests/ospf_basic_functionality/test_ospf_asbr_summary_type7_lsa.py b/tests/topotests/ospf_basic_functionality/test_ospf_asbr_summary_type7_lsa.py
index 3bd4f8b59..a4a946f2e 100644
--- a/tests/topotests/ospf_basic_functionality/test_ospf_asbr_summary_type7_lsa.py
+++ b/tests/topotests/ospf_basic_functionality/test_ospf_asbr_summary_type7_lsa.py
@@ -75,13 +75,6 @@ pytestmark = [pytest.mark.ospfd, pytest.mark.staticd]
 
 # Global variables
 topo = None
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/ospf_asbr_summary_type7_lsa.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 
 NETWORK = {
     "ipv4": [
@@ -135,28 +128,12 @@ TESTCASES =
 """
 
 
-class CreateTopo(Topo):
-    """
-    Test topology builder.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
 
     * `mod`: module name
     """
-    global topo
     testsuite_run_time = time.asctime(time.localtime(time.time()))
     logger.info("Testsuite start time: {}".format(testsuite_run_time))
     logger.info("=" * 40)
@@ -164,7 +141,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/ospf_asbr_summary_type7_lsa.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # get list of daemons needs to be started for this suite.
diff --git a/tests/topotests/ospf_basic_functionality/test_ospf_authentication.py b/tests/topotests/ospf_basic_functionality/test_ospf_authentication.py
index 6d1b8d9e9..0ddd7d517 100644
--- a/tests/topotests/ospf_basic_functionality/test_ospf_authentication.py
+++ b/tests/topotests/ospf_basic_functionality/test_ospf_authentication.py
@@ -61,13 +61,6 @@ pytestmark = [pytest.mark.ospfd]
 
 # Global variables
 topo = None
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/ospf_authentication.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 """
 TOPOOLOGY =
       Please view in a fixed-width font such as Courier.
@@ -92,28 +85,12 @@ TESTCASES =
  """
 
 
-class CreateTopo(Topo):
-    """
-    Test topology builder.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
 
     * `mod`: module name
     """
-    global topo
     testsuite_run_time = time.asctime(time.localtime(time.time()))
     logger.info("Testsuite start time: {}".format(testsuite_run_time))
     logger.info("=" * 40)
@@ -121,7 +98,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/ospf_authentication.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # get list of daemons needs to be started for this suite.
diff --git a/tests/topotests/ospf_basic_functionality/test_ospf_chaos.py b/tests/topotests/ospf_basic_functionality/test_ospf_chaos.py
index d946cca89..eade677ca 100644
--- a/tests/topotests/ospf_basic_functionality/test_ospf_chaos.py
+++ b/tests/topotests/ospf_basic_functionality/test_ospf_chaos.py
@@ -98,29 +98,6 @@ TESTCASES =
 3. Verify ospf functionality when staticd is restarted.
  """
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/ospf_chaos.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
-
-
-class CreateTopo(Topo):
-    """
-    Test topology builder.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
 
 def setup_module(mod):
     """
@@ -128,7 +105,6 @@ def setup_module(mod):
 
     * `mod`: module name
     """
-    global topo
     testsuite_run_time = time.asctime(time.localtime(time.time()))
     logger.info("Testsuite start time: {}".format(testsuite_run_time))
     logger.info("=" * 40)
@@ -136,7 +112,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/ospf_chaos.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # get list of daemons needs to be started for this suite.
diff --git a/tests/topotests/ospf_basic_functionality/test_ospf_ecmp.py b/tests/topotests/ospf_basic_functionality/test_ospf_ecmp.py
index 4c5510ca6..6c8571fa9 100644
--- a/tests/topotests/ospf_basic_functionality/test_ospf_ecmp.py
+++ b/tests/topotests/ospf_basic_functionality/test_ospf_ecmp.py
@@ -73,14 +73,6 @@ pytestmark = [pytest.mark.ospfd, pytest.mark.staticd]
 
 topo = None
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/ospf_ecmp.json".format(CWD)
-
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 
 # Global variables
 NETWORK = {
@@ -114,28 +106,12 @@ TESTCASES :
  """
 
 
-class CreateTopo(Topo):
-    """
-    Test topology builder.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
 
     * `mod`: module name
     """
-    global topo
     testsuite_run_time = time.asctime(time.localtime(time.time()))
     logger.info("Testsuite start time: {}".format(testsuite_run_time))
     logger.info("=" * 40)
@@ -143,7 +119,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/ospf_ecmp.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # get list of daemons needs to be started for this suite.
diff --git a/tests/topotests/ospf_basic_functionality/test_ospf_ecmp_lan.py b/tests/topotests/ospf_basic_functionality/test_ospf_ecmp_lan.py
index eb1c3a914..9ca46082d 100644
--- a/tests/topotests/ospf_basic_functionality/test_ospf_ecmp_lan.py
+++ b/tests/topotests/ospf_basic_functionality/test_ospf_ecmp_lan.py
@@ -76,14 +76,6 @@ pytestmark = [pytest.mark.ospfd, pytest.mark.staticd]
 # Global variables
 topo = None
 # Reading the data from JSON File for topology creation
-
-jsonFile = "{}/ospf_ecmp_lan.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
-
 NETWORK = {
     "ipv4": [
         "11.0.20.1/32",
@@ -119,28 +111,12 @@ TESTCASES =
  """
 
 
-class CreateTopo(Topo):
-    """
-    Test topology builder.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
 
     * `mod`: module name
     """
-    global topo
     testsuite_run_time = time.asctime(time.localtime(time.time()))
     logger.info("Testsuite start time: {}".format(testsuite_run_time))
     logger.info("=" * 40)
@@ -148,7 +124,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/ospf_ecmp_lan.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # get list of daemons needs to be started for this suite.
diff --git a/tests/topotests/ospf_basic_functionality/test_ospf_lan.py b/tests/topotests/ospf_basic_functionality/test_ospf_lan.py
index e7a002fb8..d85267a36 100644
--- a/tests/topotests/ospf_basic_functionality/test_ospf_lan.py
+++ b/tests/topotests/ospf_basic_functionality/test_ospf_lan.py
@@ -76,13 +76,6 @@ pytestmark = [pytest.mark.ospfd, pytest.mark.staticd]
 
 # Global variables
 topo = None
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/ospf_lan.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 
 NETWORK = {
     "ipv4": [
@@ -114,28 +107,12 @@ Testcases:
  """
 
 
-class CreateTopo(Topo):
-    """
-    Test topology builder.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
 
     * `mod`: module name
     """
-    global topo
     testsuite_run_time = time.asctime(time.localtime(time.time()))
     logger.info("Testsuite start time: {}".format(testsuite_run_time))
     logger.info("=" * 40)
@@ -143,7 +120,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/ospf_lan.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # get list of daemons needs to be started for this suite.
diff --git a/tests/topotests/ospf_basic_functionality/test_ospf_nssa.py b/tests/topotests/ospf_basic_functionality/test_ospf_nssa.py
index 5cb4bd33d..1c2b9a9dd 100644
--- a/tests/topotests/ospf_basic_functionality/test_ospf_nssa.py
+++ b/tests/topotests/ospf_basic_functionality/test_ospf_nssa.py
@@ -68,13 +68,6 @@ pytestmark = [pytest.mark.ospfd, pytest.mark.staticd]
 
 # Global variables
 topo = None
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/ospf_nssa.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 NETWORK = {
     "ipv4": [
         "11.0.20.1/32",
@@ -111,28 +104,12 @@ TESTCASES =
 """
 
 
-class CreateTopo(Topo):
-    """
-    Test topology builder.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
 
     * `mod`: module name
     """
-    global topo
     testsuite_run_time = time.asctime(time.localtime(time.time()))
     logger.info("Testsuite start time: {}".format(testsuite_run_time))
     logger.info("=" * 40)
@@ -140,7 +117,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/ospf_nssa.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # get list of daemons needs to be started for this suite.
diff --git a/tests/topotests/ospf_basic_functionality/test_ospf_p2mp.py b/tests/topotests/ospf_basic_functionality/test_ospf_p2mp.py
index 0c2619d2f..43e93e98c 100644
--- a/tests/topotests/ospf_basic_functionality/test_ospf_p2mp.py
+++ b/tests/topotests/ospf_basic_functionality/test_ospf_p2mp.py
@@ -69,19 +69,12 @@ from lib.ospf import (
     verify_ospf_database,
 )
 
-pytestmark = [pytest.mark.ospfd, pytest.mark.staticd]
 
+pytestmark = [pytest.mark.ospfd, pytest.mark.staticd]
 
 # Global variables
 topo = None
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/ospf_p2mp.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 
 """
 TOPOOLOGY =
@@ -104,28 +97,12 @@ TESTCASES =
  """
 
 
-class CreateTopo(Topo):
-    """
-    Test topology builder.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
 
     * `mod`: module name
     """
-    global topo
     testsuite_run_time = time.asctime(time.localtime(time.time()))
     logger.info("Testsuite start time: {}".format(testsuite_run_time))
     logger.info("=" * 40)
@@ -133,7 +110,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/ospf_p2mp.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # get list of daemons needs to be started for this suite.
diff --git a/tests/topotests/ospf_basic_functionality/test_ospf_routemaps.py b/tests/topotests/ospf_basic_functionality/test_ospf_routemaps.py
index 34abd0dc4..5620ce60a 100644
--- a/tests/topotests/ospf_basic_functionality/test_ospf_routemaps.py
+++ b/tests/topotests/ospf_basic_functionality/test_ospf_routemaps.py
@@ -71,13 +71,6 @@ pytestmark = [pytest.mark.ospfd, pytest.mark.staticd]
 
 # Global variables
 topo = None
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/ospf_routemaps.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 
 NETWORK = {
     "ipv4": [
@@ -124,28 +117,12 @@ TESTCASES =
  """
 
 
-class CreateTopo(Topo):
-    """
-    Test topology builder.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
 
     * `mod`: module name
     """
-    global topo
     testsuite_run_time = time.asctime(time.localtime(time.time()))
     logger.info("Testsuite start time: {}".format(testsuite_run_time))
     logger.info("=" * 40)
@@ -153,7 +130,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/ospf_routemaps.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # get list of daemons needs to be started for this suite.
diff --git a/tests/topotests/ospf_basic_functionality/test_ospf_rte_calc.py b/tests/topotests/ospf_basic_functionality/test_ospf_rte_calc.py
index 9f05f396a..d89864ac4 100644
--- a/tests/topotests/ospf_basic_functionality/test_ospf_rte_calc.py
+++ b/tests/topotests/ospf_basic_functionality/test_ospf_rte_calc.py
@@ -75,14 +75,6 @@ topo = None
 # number of retries.
 nretry = 5
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/ospf_rte_calc.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
-
 NETWORK = {
     "ipv4": [
         "11.0.20.1/32",
@@ -115,28 +107,12 @@ TESTCASES = """
 """
 
 
-class CreateTopo(Topo):
-    """
-    Test topology builder.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
 
     * `mod`: module name
     """
-    global topo
     testsuite_run_time = time.asctime(time.localtime(time.time()))
     logger.info("Testsuite start time: {}".format(testsuite_run_time))
     logger.info("=" * 40)
@@ -144,7 +120,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/ospf_rte_calc.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # get list of daemons needs to be started for this suite.
diff --git a/tests/topotests/ospf_basic_functionality/test_ospf_single_area.py b/tests/topotests/ospf_basic_functionality/test_ospf_single_area.py
index 2773c01ff..4bbc9099d 100644
--- a/tests/topotests/ospf_basic_functionality/test_ospf_single_area.py
+++ b/tests/topotests/ospf_basic_functionality/test_ospf_single_area.py
@@ -73,13 +73,6 @@ pytestmark = [pytest.mark.ospfd, pytest.mark.staticd]
 # Global variables
 topo = None
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/ospf_single_area.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 
 """
 TOPOOLOGY =
@@ -106,28 +99,12 @@ TESTCASES =
  """
 
 
-class CreateTopo(Topo):
-    """
-    Test topology builder.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
 
     * `mod`: module name
     """
-    global topo
     testsuite_run_time = time.asctime(time.localtime(time.time()))
     logger.info("Testsuite start time: {}".format(testsuite_run_time))
     logger.info("=" * 40)
@@ -135,7 +112,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/ospf_single_area.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # get list of daemons needs to be started for this suite.
diff --git a/tests/topotests/ospf_dual_stack/test_ospf_dual_stack.py b/tests/topotests/ospf_dual_stack/test_ospf_dual_stack.py
index f4d98fddb..fda9892f2 100644
--- a/tests/topotests/ospf_dual_stack/test_ospf_dual_stack.py
+++ b/tests/topotests/ospf_dual_stack/test_ospf_dual_stack.py
@@ -48,29 +48,10 @@ pytestmark = [pytest.mark.ospfd, pytest.mark.staticd]
 # Global variables
 topo = None
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/test_ospf_dual_stack.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
-
-
-class CreateTopo(Topo):
-    """Test topology builder."""
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
 
 
 def setup_module(mod):
     """Sets up the pytest environment."""
-    global topo
     testsuite_run_time = time.asctime(time.localtime(time.time()))
     logger.info("Testsuite start time: {}".format(testsuite_run_time))
     logger.info("=" * 40)
@@ -78,7 +59,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/test_ospf_dual_stack.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # get list of daemons needs to be started for this suite.
diff --git a/tests/topotests/ospf_gr_helper/test_ospf_gr_helper.py b/tests/topotests/ospf_gr_helper/test_ospf_gr_helper.py
index 536382213..6e3147bd0 100644
--- a/tests/topotests/ospf_gr_helper/test_ospf_gr_helper.py
+++ b/tests/topotests/ospf_gr_helper/test_ospf_gr_helper.py
@@ -37,7 +37,6 @@ sys.path.append(os.path.join(CWD, "../"))
 
 # pylint: disable=C0413
 # Import topogen and topotest helpers
-from mininet.topo import Topo
 from lib.topogen import Topogen, get_topogen
 
 # Import topoJson from lib, to create topology and initial configuration
@@ -76,14 +75,6 @@ intf = None
 intf1 = None
 pkt = None
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/ospf_gr_helper.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
-
 """
 Topology:
 
@@ -118,21 +109,6 @@ TC8.    Verify helper functionality when dut is helping RR and new grace lsa
 """
 
 
-class CreateTopo(Topo):
-    """
-    Test topology builder.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
@@ -147,7 +123,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/ospf_gr_helper.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # get list of daemons needs to be started for this suite.
@@ -169,7 +148,7 @@ def setup_module(mod):
         ospf_covergence
     )
 
-    sw_name = topo["switches"].keys()[0]
+    sw_name = "s1"
     intf = topo["routers"]["r0"]["links"][sw_name]["interface"]
     intf1 = topo["routers"]["r1"]["links"][sw_name]["interface"]
     pkt = topo["routers"]["r1"]["opq_lsa_hex"]
diff --git a/tests/topotests/ospf_gr_topo1/test_ospf_gr_topo1.py b/tests/topotests/ospf_gr_topo1/test_ospf_gr_topo1.py
index 3520cdf24..0a6e1ea2f 100755
--- a/tests/topotests/ospf_gr_topo1/test_ospf_gr_topo1.py
+++ b/tests/topotests/ospf_gr_topo1/test_ospf_gr_topo1.py
@@ -100,56 +100,50 @@ pytestmark = [pytest.mark.ospfd]
 outputs = {}
 
 
-class TemplateTopo(Topo):
-    "Test topology builder"
+def build_topo(tgen):
+    #
+    # Define FRR Routers
+    #
+    for router in ["rt1", "rt2", "rt3", "rt4", "rt5", "rt6", "rt7"]:
+        tgen.add_router(router)
 
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+    #
+    # Define connections
+    #
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["rt1"], nodeif="eth-rt2")
+    switch.add_link(tgen.gears["rt2"], nodeif="eth-rt1")
 
-        #
-        # Define FRR Routers
-        #
-        for router in ["rt1", "rt2", "rt3", "rt4", "rt5", "rt6", "rt7"]:
-            tgen.add_router(router)
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["rt1"], nodeif="stub1")
 
-        #
-        # Define connections
-        #
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["rt1"], nodeif="eth-rt2")
-        switch.add_link(tgen.gears["rt2"], nodeif="eth-rt1")
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["rt2"], nodeif="eth-rt3")
+    switch.add_link(tgen.gears["rt3"], nodeif="eth-rt2")
 
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["rt1"], nodeif="stub1")
+    switch = tgen.add_switch("s4")
+    switch.add_link(tgen.gears["rt3"], nodeif="eth-rt4")
+    switch.add_link(tgen.gears["rt4"], nodeif="eth-rt3")
 
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["rt2"], nodeif="eth-rt3")
-        switch.add_link(tgen.gears["rt3"], nodeif="eth-rt2")
+    switch = tgen.add_switch("s5")
+    switch.add_link(tgen.gears["rt3"], nodeif="eth-rt6")
+    switch.add_link(tgen.gears["rt6"], nodeif="eth-rt3")
 
-        switch = tgen.add_switch("s4")
-        switch.add_link(tgen.gears["rt3"], nodeif="eth-rt4")
-        switch.add_link(tgen.gears["rt4"], nodeif="eth-rt3")
+    switch = tgen.add_switch("s6")
+    switch.add_link(tgen.gears["rt4"], nodeif="eth-rt5")
+    switch.add_link(tgen.gears["rt5"], nodeif="eth-rt4")
 
-        switch = tgen.add_switch("s5")
-        switch.add_link(tgen.gears["rt3"], nodeif="eth-rt6")
-        switch.add_link(tgen.gears["rt6"], nodeif="eth-rt3")
+    switch = tgen.add_switch("s7")
+    switch.add_link(tgen.gears["rt6"], nodeif="eth-rt7")
+    switch.add_link(tgen.gears["rt7"], nodeif="eth-rt6")
 
-        switch = tgen.add_switch("s6")
-        switch.add_link(tgen.gears["rt4"], nodeif="eth-rt5")
-        switch.add_link(tgen.gears["rt5"], nodeif="eth-rt4")
-
-        switch = tgen.add_switch("s7")
-        switch.add_link(tgen.gears["rt6"], nodeif="eth-rt7")
-        switch.add_link(tgen.gears["rt7"], nodeif="eth-rt6")
-
-        switch = tgen.add_switch("s8")
-        switch.add_link(tgen.gears["rt7"], nodeif="stub1")
+    switch = tgen.add_switch("s8")
+    switch.add_link(tgen.gears["rt7"], nodeif="stub1")
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/ospf_sr_te_topo1/test_ospf_sr_te_topo1.py b/tests/topotests/ospf_sr_te_topo1/test_ospf_sr_te_topo1.py
index 6146178d8..cf8914111 100755
--- a/tests/topotests/ospf_sr_te_topo1/test_ospf_sr_te_topo1.py
+++ b/tests/topotests/ospf_sr_te_topo1/test_ospf_sr_te_topo1.py
@@ -98,64 +98,60 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bgpd, pytest.mark.ospfd, pytest.mark.pathd]
 
 
-class TemplateTopo(Topo):
-    "Test topology builder"
+def build_topo(tgen):
+    "Build function"
 
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+    #
+    # Define FRR Routers
+    #
+    for router in ["rt1", "rt2", "rt3", "rt4", "rt5", "rt6", "dst"]:
+        tgen.add_router(router)
 
-        #
-        # Define FRR Routers
-        #
-        for router in ["rt1", "rt2", "rt3", "rt4", "rt5", "rt6", "dst"]:
-            tgen.add_router(router)
+    #
+    # Define connections
+    #
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["rt1"], nodeif="eth-sw1")
+    switch.add_link(tgen.gears["rt2"], nodeif="eth-sw1")
+    #switch.add_link(tgen.gears["rt3"], nodeif="eth-sw1")
 
-        #
-        # Define connections
-        #
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["rt1"], nodeif="eth-sw1")
-        switch.add_link(tgen.gears["rt2"], nodeif="eth-sw1")
-        #switch.add_link(tgen.gears["rt3"], nodeif="eth-sw1")
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["rt2"], nodeif="eth-rt4-1")
+    switch.add_link(tgen.gears["rt4"], nodeif="eth-rt2-1")
 
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["rt2"], nodeif="eth-rt4-1")
-        switch.add_link(tgen.gears["rt4"], nodeif="eth-rt2-1")
+    #switch = tgen.add_switch("s3")
+    #switch.add_link(tgen.gears["rt2"], nodeif="eth-rt4-2")
+    #switch.add_link(tgen.gears["rt4"], nodeif="eth-rt2-2")
 
-        #switch = tgen.add_switch("s3")
-        #switch.add_link(tgen.gears["rt2"], nodeif="eth-rt4-2")
-        #switch.add_link(tgen.gears["rt4"], nodeif="eth-rt2-2")
+    switch = tgen.add_switch("s4")
+    switch.add_link(tgen.gears["rt3"], nodeif="eth-rt5-1")
+    switch.add_link(tgen.gears["rt5"], nodeif="eth-rt3-1")
 
-        switch = tgen.add_switch("s4")
-        switch.add_link(tgen.gears["rt3"], nodeif="eth-rt5-1")
-        switch.add_link(tgen.gears["rt5"], nodeif="eth-rt3-1")
+    switch = tgen.add_switch("s5")
+    switch.add_link(tgen.gears["rt3"], nodeif="eth-rt5-2")
+    switch.add_link(tgen.gears["rt5"], nodeif="eth-rt3-2")
 
-        switch = tgen.add_switch("s5")
-        switch.add_link(tgen.gears["rt3"], nodeif="eth-rt5-2")
-        switch.add_link(tgen.gears["rt5"], nodeif="eth-rt3-2")
+    switch = tgen.add_switch("s6")
+    switch.add_link(tgen.gears["rt4"], nodeif="eth-rt5")
+    switch.add_link(tgen.gears["rt5"], nodeif="eth-rt4")
 
-        switch = tgen.add_switch("s6")
-        switch.add_link(tgen.gears["rt4"], nodeif="eth-rt5")
-        switch.add_link(tgen.gears["rt5"], nodeif="eth-rt4")
+    switch = tgen.add_switch("s7")
+    switch.add_link(tgen.gears["rt4"], nodeif="eth-rt6")
+    switch.add_link(tgen.gears["rt6"], nodeif="eth-rt4")
 
-        switch = tgen.add_switch("s7")
-        switch.add_link(tgen.gears["rt4"], nodeif="eth-rt6")
-        switch.add_link(tgen.gears["rt6"], nodeif="eth-rt4")
+    switch = tgen.add_switch("s8")
+    switch.add_link(tgen.gears["rt5"], nodeif="eth-rt6")
+    switch.add_link(tgen.gears["rt6"], nodeif="eth-rt5")
 
-        switch = tgen.add_switch("s8")
-        switch.add_link(tgen.gears["rt5"], nodeif="eth-rt6")
-        switch.add_link(tgen.gears["rt6"], nodeif="eth-rt5")
-
-        switch = tgen.add_switch("s9")
-        switch.add_link(tgen.gears["rt6"], nodeif="eth-dst")
-        switch.add_link(tgen.gears["dst"], nodeif="eth-rt6")
+    switch = tgen.add_switch("s9")
+    switch.add_link(tgen.gears["rt6"], nodeif="eth-dst")
+    switch.add_link(tgen.gears["dst"], nodeif="eth-rt6")
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
 
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
 
     frrdir = tgen.config.get(tgen.CONFIG_SECTION, "frrdir")
     if not os.path.isfile(os.path.join(frrdir, "pathd")):
diff --git a/tests/topotests/ospf_sr_topo1/test_ospf_sr_topo1.py b/tests/topotests/ospf_sr_topo1/test_ospf_sr_topo1.py
index 3f448d4bf..60c87cbb5 100644
--- a/tests/topotests/ospf_sr_topo1/test_ospf_sr_topo1.py
+++ b/tests/topotests/ospf_sr_topo1/test_ospf_sr_topo1.py
@@ -87,59 +87,55 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.ospfd]
 
 
-class TemplateTopo(Topo):
-    "Test topology builder"
+def build_topo(tgen):
+    "Build function"
 
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+    #
+    # Define FRR Routers
+    #
+    for router in ["rt1", "rt2", "rt3", "rt4", "rt5", "rt6"]:
+        tgen.add_router(router)
 
-        #
-        # Define FRR Routers
-        #
-        for router in ["rt1", "rt2", "rt3", "rt4", "rt5", "rt6"]:
-            tgen.add_router(router)
+    #
+    # Define connections
+    #
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["rt1"], nodeif="eth-sw1")
+    switch.add_link(tgen.gears["rt2"], nodeif="eth-sw1")
+    switch.add_link(tgen.gears["rt3"], nodeif="eth-sw1")
 
-        #
-        # Define connections
-        #
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["rt1"], nodeif="eth-sw1")
-        switch.add_link(tgen.gears["rt2"], nodeif="eth-sw1")
-        switch.add_link(tgen.gears["rt3"], nodeif="eth-sw1")
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["rt2"], nodeif="eth-rt4-1")
+    switch.add_link(tgen.gears["rt4"], nodeif="eth-rt2-1")
 
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["rt2"], nodeif="eth-rt4-1")
-        switch.add_link(tgen.gears["rt4"], nodeif="eth-rt2-1")
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["rt2"], nodeif="eth-rt4-2")
+    switch.add_link(tgen.gears["rt4"], nodeif="eth-rt2-2")
 
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["rt2"], nodeif="eth-rt4-2")
-        switch.add_link(tgen.gears["rt4"], nodeif="eth-rt2-2")
+    switch = tgen.add_switch("s4")
+    switch.add_link(tgen.gears["rt3"], nodeif="eth-rt5-1")
+    switch.add_link(tgen.gears["rt5"], nodeif="eth-rt3-1")
 
-        switch = tgen.add_switch("s4")
-        switch.add_link(tgen.gears["rt3"], nodeif="eth-rt5-1")
-        switch.add_link(tgen.gears["rt5"], nodeif="eth-rt3-1")
+    switch = tgen.add_switch("s5")
+    switch.add_link(tgen.gears["rt3"], nodeif="eth-rt5-2")
+    switch.add_link(tgen.gears["rt5"], nodeif="eth-rt3-2")
 
-        switch = tgen.add_switch("s5")
-        switch.add_link(tgen.gears["rt3"], nodeif="eth-rt5-2")
-        switch.add_link(tgen.gears["rt5"], nodeif="eth-rt3-2")
+    switch = tgen.add_switch("s6")
+    switch.add_link(tgen.gears["rt4"], nodeif="eth-rt5")
+    switch.add_link(tgen.gears["rt5"], nodeif="eth-rt4")
 
-        switch = tgen.add_switch("s6")
-        switch.add_link(tgen.gears["rt4"], nodeif="eth-rt5")
-        switch.add_link(tgen.gears["rt5"], nodeif="eth-rt4")
+    switch = tgen.add_switch("s7")
+    switch.add_link(tgen.gears["rt4"], nodeif="eth-rt6")
+    switch.add_link(tgen.gears["rt6"], nodeif="eth-rt4")
 
-        switch = tgen.add_switch("s7")
-        switch.add_link(tgen.gears["rt4"], nodeif="eth-rt6")
-        switch.add_link(tgen.gears["rt6"], nodeif="eth-rt4")
-
-        switch = tgen.add_switch("s8")
-        switch.add_link(tgen.gears["rt5"], nodeif="eth-rt6")
-        switch.add_link(tgen.gears["rt6"], nodeif="eth-rt5")
+    switch = tgen.add_switch("s8")
+    switch.add_link(tgen.gears["rt5"], nodeif="eth-rt6")
+    switch.add_link(tgen.gears["rt6"], nodeif="eth-rt5")
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/ospf_suppress_fa/test_ospf_suppress_fa.py b/tests/topotests/ospf_suppress_fa/test_ospf_suppress_fa.py
index 2975e5864..2dcdcba58 100644
--- a/tests/topotests/ospf_suppress_fa/test_ospf_suppress_fa.py
+++ b/tests/topotests/ospf_suppress_fa/test_ospf_suppress_fa.py
@@ -53,33 +53,29 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.ospfd]
 
 
-class NetworkTopo(Topo):
-    "OSPF topology builder"
+def build_topo(tgen):
+    "Build function"
 
-    def build(self, *_args, **_opts):
-        "Build function"
 
-        tgen = get_topogen(self)
+    # Create routers
+    for router in range(1, 4):
+        tgen.add_router("r{}".format(router))
 
-        # Create routers
-        for router in range(1, 4):
-            tgen.add_router("r{}".format(router))
+    # R1-R2 backbone area
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
-        # R1-R2 backbone area
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
-
-        # R2-R3 NSSA area
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
+    # R2-R3 NSSA area
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
 
-    tgen = Topogen(NetworkTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     # This is a sample of configuration loading.
diff --git a/tests/topotests/ospf_te_topo1/test_ospf_te_topo1.py b/tests/topotests/ospf_te_topo1/test_ospf_te_topo1.py
index 1678287bb..a8bb2f699 100644
--- a/tests/topotests/ospf_te_topo1/test_ospf_te_topo1.py
+++ b/tests/topotests/ospf_te_topo1/test_ospf_te_topo1.py
@@ -80,38 +80,34 @@ import pytest
 pytestmark = [pytest.mark.ospfd]
 
 
-class OspfTeTopo(Topo):
-    "Test topology builder"
+def build_topo(tgen):
+    "Build function"
 
-    def build(self, *args, **kwargs):
-        "Build function"
-        tgen = get_topogen(self)
+    # Create 4 routers
+    for routern in range(1, 5):
+        tgen.add_router("r{}".format(routern))
 
-        # Create 4 routers
-        for routern in range(1, 5):
-            tgen.add_router("r{}".format(routern))
+    # Interconect router 1 and 2 with 2 links
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
-        # Interconect router 1 and 2 with 2 links
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    # Interconect router 3 and 2
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["r3"])
+    switch.add_link(tgen.gears["r2"])
 
-        # Interconect router 3 and 2
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["r3"])
-        switch.add_link(tgen.gears["r2"])
+    # Interconect router 4 and 2
+    switch = tgen.add_switch("s4")
+    switch.add_link(tgen.gears["r4"])
+    switch.add_link(tgen.gears["r2"])
 
-        # Interconect router 4 and 2
-        switch = tgen.add_switch("s4")
-        switch.add_link(tgen.gears["r4"])
-        switch.add_link(tgen.gears["r2"])
-
-        # Interconnect router 3 with next AS
-        switch = tgen.add_switch("s5")
-        switch.add_link(tgen.gears["r3"])
+    # Interconnect router 3 with next AS
+    switch = tgen.add_switch("s5")
+    switch.add_link(tgen.gears["r3"])
 
 
 def setup_module(mod):
@@ -119,7 +115,7 @@ def setup_module(mod):
 
     logger.info("\n\n---- Starting OSPF TE tests ----\n")
 
-    tgen = Topogen(OspfTeTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/ospf_tilfa_topo1/test_ospf_tilfa_topo1.py b/tests/topotests/ospf_tilfa_topo1/test_ospf_tilfa_topo1.py
index 956e2ab0a..97ccdbf37 100644
--- a/tests/topotests/ospf_tilfa_topo1/test_ospf_tilfa_topo1.py
+++ b/tests/topotests/ospf_tilfa_topo1/test_ospf_tilfa_topo1.py
@@ -74,46 +74,42 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.ospfd]
 
 
-class TemplateTopo(Topo):
-    "Test topology builder"
+def build_topo(tgen):
+    "Build function"
 
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+    #
+    # Define FRR Routers
+    #
+    for router in ["rt1", "rt2", "rt3", "rt4", "rt5"]:
+        tgen.add_router(router)
 
-        #
-        # Define FRR Routers
-        #
-        for router in ["rt1", "rt2", "rt3", "rt4", "rt5"]:
-            tgen.add_router(router)
+    #
+    # Define connections
+    #
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["rt1"], nodeif="eth-rt2")
+    switch.add_link(tgen.gears["rt2"], nodeif="eth-rt1")
 
-        #
-        # Define connections
-        #
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["rt1"], nodeif="eth-rt2")
-        switch.add_link(tgen.gears["rt2"], nodeif="eth-rt1")
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["rt1"], nodeif="eth-rt3")
+    switch.add_link(tgen.gears["rt3"], nodeif="eth-rt1")
 
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["rt1"], nodeif="eth-rt3")
-        switch.add_link(tgen.gears["rt3"], nodeif="eth-rt1")
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["rt2"], nodeif="eth-rt4")
+    switch.add_link(tgen.gears["rt4"], nodeif="eth-rt2")
 
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["rt2"], nodeif="eth-rt4")
-        switch.add_link(tgen.gears["rt4"], nodeif="eth-rt2")
+    switch = tgen.add_switch("s4")
+    switch.add_link(tgen.gears["rt3"], nodeif="eth-rt5")
+    switch.add_link(tgen.gears["rt5"], nodeif="eth-rt3")
 
-        switch = tgen.add_switch("s4")
-        switch.add_link(tgen.gears["rt3"], nodeif="eth-rt5")
-        switch.add_link(tgen.gears["rt5"], nodeif="eth-rt3")
-
-        switch = tgen.add_switch("s5")
-        switch.add_link(tgen.gears["rt4"], nodeif="eth-rt5")
-        switch.add_link(tgen.gears["rt5"], nodeif="eth-rt4")
+    switch = tgen.add_switch("s5")
+    switch.add_link(tgen.gears["rt4"], nodeif="eth-rt5")
+    switch.add_link(tgen.gears["rt5"], nodeif="eth-rt4")
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/ospf_topo1/test_ospf_topo1.py b/tests/topotests/ospf_topo1/test_ospf_topo1.py
index 50992503e..175b75f90 100644
--- a/tests/topotests/ospf_topo1/test_ospf_topo1.py
+++ b/tests/topotests/ospf_topo1/test_ospf_topo1.py
@@ -48,48 +48,44 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.ospfd]
 
 
-class OSPFTopo(Topo):
-    "Test topology builder"
+def build_topo(tgen):
+    "Build function"
 
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+    # Create 4 routers
+    for routern in range(1, 5):
+        tgen.add_router("r{}".format(routern))
 
-        # Create 4 routers
-        for routern in range(1, 5):
-            tgen.add_router("r{}".format(routern))
+    # Create a empty network for router 1
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
 
-        # Create a empty network for router 1
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
+    # Create a empty network for router 2
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r2"])
 
-        # Create a empty network for router 2
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["r2"])
+    # Interconect router 1, 2 and 3
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
 
-        # Interconect router 1, 2 and 3
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
+    # Create empty netowrk for router3
+    switch = tgen.add_switch("s4")
+    switch.add_link(tgen.gears["r3"])
 
-        # Create empty netowrk for router3
-        switch = tgen.add_switch("s4")
-        switch.add_link(tgen.gears["r3"])
+    # Interconect router 3 and 4
+    switch = tgen.add_switch("s5")
+    switch.add_link(tgen.gears["r3"])
+    switch.add_link(tgen.gears["r4"])
 
-        # Interconect router 3 and 4
-        switch = tgen.add_switch("s5")
-        switch.add_link(tgen.gears["r3"])
-        switch.add_link(tgen.gears["r4"])
-
-        # Create a empty network for router 4
-        switch = tgen.add_switch("s6")
-        switch.add_link(tgen.gears["r4"])
+    # Create a empty network for router 4
+    switch = tgen.add_switch("s6")
+    switch.add_link(tgen.gears["r4"])
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(OSPFTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     ospf6_config = "ospf6d.conf"
diff --git a/tests/topotests/ospf_topo1_vrf/test_ospf_topo1_vrf.py b/tests/topotests/ospf_topo1_vrf/test_ospf_topo1_vrf.py
index 711f76c5c..c83c91668 100644
--- a/tests/topotests/ospf_topo1_vrf/test_ospf_topo1_vrf.py
+++ b/tests/topotests/ospf_topo1_vrf/test_ospf_topo1_vrf.py
@@ -48,39 +48,35 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.ospfd]
 
 
-class OSPFTopo(Topo):
-    "Test topology builder"
+def build_topo(tgen):
+    "Build function"
 
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+    # Create 3 routers
+    for routern in range(1, 4):
+        tgen.add_router("r{}".format(routern))
 
-        # Create 3 routers
-        for routern in range(1, 4):
-            tgen.add_router("r{}".format(routern))
+    # Create a empty network for router 1
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
 
-        # Create a empty network for router 1
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
+    # Create a empty network for router 2
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r2"])
 
-        # Create a empty network for router 2
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["r2"])
+    # Interconect router 1, 2 and 3
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
 
-        # Interconect router 1, 2 and 3
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
-
-        # Create empty netowrk for router3
-        switch = tgen.add_switch("s4")
-        switch.add_link(tgen.gears["r3"])
+    # Create empty netowrk for router3
+    switch = tgen.add_switch("s4")
+    switch.add_link(tgen.gears["r3"])
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(OSPFTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/ospf_topo2/test_ospf_topo2.py b/tests/topotests/ospf_topo2/test_ospf_topo2.py
index 38d424c90..696396d68 100644
--- a/tests/topotests/ospf_topo2/test_ospf_topo2.py
+++ b/tests/topotests/ospf_topo2/test_ospf_topo2.py
@@ -49,34 +49,32 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.ospfd]
 
 
-class OSPFTopo(Topo):
-    "Test topology builder"
+CWD = os.path.dirname(os.path.realpath(__file__))
 
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+def build_topo(tgen):
+    "Build function"
 
-        # Create 4 routers
-        for routern in range(1, 3):
-            tgen.add_router("r{}".format(routern))
+    # Create 4 routers
+    for routern in range(1, 3):
+        tgen.add_router("r{}".format(routern))
 
-        # Create a empty network for router 1
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
+    # Create a empty network for router 1
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
 
-        # Create a empty network for router 2
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["r2"])
+    # Create a empty network for router 2
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r2"])
 
-        # Interconect router 1, 2
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    # Interconect router 1, 2
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(OSPFTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/ospfv3_basic_functionality/test_ospfv3_asbr_summary_topo1.py b/tests/topotests/ospfv3_basic_functionality/test_ospfv3_asbr_summary_topo1.py
index c76da39ca..f2158c36e 100644
--- a/tests/topotests/ospfv3_basic_functionality/test_ospfv3_asbr_summary_topo1.py
+++ b/tests/topotests/ospfv3_basic_functionality/test_ospfv3_asbr_summary_topo1.py
@@ -75,13 +75,6 @@ from lib.ospf import (
 
 # Global variables
 topo = None
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/ospfv3_asbr_summary_topo1.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 
 NETWORK = {
     "ipv4": [
@@ -149,28 +142,12 @@ TESTCASES =
 """
 
 
-class CreateTopo(Topo):
-    """
-    Test topology builder.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
 
     * `mod`: module name
     """
-    global topo
     testsuite_run_time = time.asctime(time.localtime(time.time()))
     logger.info("Testsuite start time: {}".format(testsuite_run_time))
     logger.info("=" * 40)
@@ -178,7 +155,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/ospfv3_asbr_summary_topo1.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # get list of daemons needs to be started for this suite.
diff --git a/tests/topotests/ospfv3_basic_functionality/test_ospfv3_ecmp.py b/tests/topotests/ospfv3_basic_functionality/test_ospfv3_ecmp.py
index 6bfe4f199..50f05a2ec 100644
--- a/tests/topotests/ospfv3_basic_functionality/test_ospfv3_ecmp.py
+++ b/tests/topotests/ospfv3_basic_functionality/test_ospfv3_ecmp.py
@@ -78,14 +78,6 @@ pytestmark = [pytest.mark.ospfd, pytest.mark.staticd]
 # Global variables
 topo = None
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/ospfv3_ecmp.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
-
 NETWORK = {
     "ipv4": [
         "11.0.20.1/32",
@@ -118,28 +110,12 @@ TESTCASES :
  """
 
 
-class CreateTopo(Topo):
-    """
-    Test topology builder.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
 
     * `mod`: module name
     """
-    global topo
     testsuite_run_time = time.asctime(time.localtime(time.time()))
     logger.info("Testsuite start time: {}".format(testsuite_run_time))
     logger.info("=" * 40)
@@ -147,7 +123,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/ospfv3_ecmp.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # get list of daemons needs to be started for this suite.
diff --git a/tests/topotests/ospfv3_basic_functionality/test_ospfv3_routemaps.py b/tests/topotests/ospfv3_basic_functionality/test_ospfv3_routemaps.py
index af1017c6b..9d944f4d9 100644
--- a/tests/topotests/ospfv3_basic_functionality/test_ospfv3_routemaps.py
+++ b/tests/topotests/ospfv3_basic_functionality/test_ospfv3_routemaps.py
@@ -78,13 +78,6 @@ pytestmark = [pytest.mark.ospfd, pytest.mark.staticd]
 # Global variables
 topo = None
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/ospfv3_routemaps.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 
 NETWORK = {
     "ipv4": [
@@ -131,28 +124,12 @@ TESTCASES =
  """
 
 
-class CreateTopo(Topo):
-    """
-    Test topology builder.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
 
     * `mod`: module name
     """
-    global topo
     testsuite_run_time = time.asctime(time.localtime(time.time()))
     logger.info("Testsuite start time: {}".format(testsuite_run_time))
     logger.info("=" * 40)
@@ -160,7 +137,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/ospfv3_routemaps.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # get list of daemons needs to be started for this suite.
diff --git a/tests/topotests/ospfv3_basic_functionality/test_ospfv3_rte_calc.py b/tests/topotests/ospfv3_basic_functionality/test_ospfv3_rte_calc.py
index d16cbb76f..f4dc8dc09 100644
--- a/tests/topotests/ospfv3_basic_functionality/test_ospfv3_rte_calc.py
+++ b/tests/topotests/ospfv3_basic_functionality/test_ospfv3_rte_calc.py
@@ -80,14 +80,6 @@ pytestmark = [pytest.mark.ospfd, pytest.mark.staticd]
 # Global variables
 topo = None
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/ospfv3_rte_calc.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
-
 NETWORK = {
     "ipv6": [
         "11.0.20.1/32",
@@ -119,28 +111,12 @@ TESTCASES = """
 """
 
 
-class CreateTopo(Topo):
-    """
-    Test topology builder.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
 
     * `mod`: module name
     """
-    global topo
     testsuite_run_time = time.asctime(time.localtime(time.time()))
     logger.info("Testsuite start time: {}".format(testsuite_run_time))
     logger.info("=" * 40)
@@ -148,7 +124,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/ospfv3_rte_calc.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # get list of daemons needs to be started for this suite.
diff --git a/tests/topotests/ospfv3_basic_functionality/test_ospfv3_single_area.py b/tests/topotests/ospfv3_basic_functionality/test_ospfv3_single_area.py
index 22593baba..969e9c45b 100644
--- a/tests/topotests/ospfv3_basic_functionality/test_ospfv3_single_area.py
+++ b/tests/topotests/ospfv3_basic_functionality/test_ospfv3_single_area.py
@@ -78,14 +78,6 @@ pytestmark = [pytest.mark.ospfd, pytest.mark.staticd]
 # Global variables
 topo = None
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/ospfv3_single_area.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
-
 """
 TOPOOLOGY =
       Please view in a fixed-width font such as Courier.
@@ -111,28 +103,12 @@ TESTCASES =
  """
 
 
-class CreateTopo(Topo):
-    """
-    Test topology builder.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment
 
     * `mod`: module name
     """
-    global topo
     testsuite_run_time = time.asctime(time.localtime(time.time()))
     logger.info("Testsuite start time: {}".format(testsuite_run_time))
     logger.info("=" * 40)
@@ -140,7 +116,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/ospfv3_single_area.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # get list of daemons needs to be started for this suite.
diff --git a/tests/topotests/pbr_topo1/test_pbr_topo1.py b/tests/topotests/pbr_topo1/test_pbr_topo1.py
index 494e27a2a..304a2dd0c 100644
--- a/tests/topotests/pbr_topo1/test_pbr_topo1.py
+++ b/tests/topotests/pbr_topo1/test_pbr_topo1.py
@@ -58,22 +58,18 @@ pytestmark = [pytest.mark.pbrd]
 #####################################################
 
 
-class NetworkTopo(Topo):
-    "PBR Topology 1"
+def build_topo(tgen):
+    "Build function"
 
-    def build(self, **_opts):
-        "Build function"
 
-        tgen = get_topogen(self)
+    # Populate routers
+    for routern in range(1, 2):
+        tgen.add_router("r{}".format(routern))
 
-        # Populate routers
-        for routern in range(1, 2):
-            tgen.add_router("r{}".format(routern))
-
-        # Populate switches
-        for switchn in range(1, 6):
-            switch = tgen.add_switch("sw{}".format(switchn))
-            switch.add_link(tgen.gears["r1"])
+    # Populate switches
+    for switchn in range(1, 6):
+        switch = tgen.add_switch("sw{}".format(switchn))
+        switch.add_link(tgen.gears["r1"])
 
 
 #####################################################
@@ -85,7 +81,7 @@ class NetworkTopo(Topo):
 
 def setup_module(module):
     "Setup topology"
-    tgen = Topogen(NetworkTopo, module.__name__)
+    tgen = Topogen(build_topo, module.__name__)
     tgen.start_topology()
 
     krel = platform.release()
diff --git a/tests/topotests/pim_basic/test_pim.py b/tests/topotests/pim_basic/test_pim.py
index e921b37b6..c346a77c0 100644
--- a/tests/topotests/pim_basic/test_pim.py
+++ b/tests/topotests/pim_basic/test_pim.py
@@ -46,48 +46,46 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.pimd]
 
 
-class PIMTopo(Topo):
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
-
-        for routern in range(1, 4):
-            tgen.add_router("r{}".format(routern))
-
-        tgen.add_router("rp")
-
-        #   rp ------ r1 -------- r2
-        #              \
-        #               --------- r3
-        # r1 -> .1
-        # r2 -> .2
-        # rp -> .3
-        # r3 -> .4
-        # loopback network is 10.254.0.X/32
-        #
-        # r1 <- sw1 -> r2
-        # r1-eth0 <-> r2-eth0
-        # 10.0.20.0/24
-        sw = tgen.add_switch("sw1")
-        sw.add_link(tgen.gears["r1"])
-        sw.add_link(tgen.gears["r2"])
-
-        # r1 <- sw2 -> rp
-        # r1-eth1 <-> rp-eth0
-        # 10.0.30.0/24
-        sw = tgen.add_switch("sw2")
-        sw.add_link(tgen.gears["r1"])
-        sw.add_link(tgen.gears["rp"])
-
-        # 10.0.40.0/24
-        sw = tgen.add_switch("sw3")
-        sw.add_link(tgen.gears["r1"])
-        sw.add_link(tgen.gears["r3"])
+def build_topo(tgen):
+    "Build function"
+
+    for routern in range(1, 4):
+        tgen.add_router("r{}".format(routern))
+
+    tgen.add_router("rp")
+
+    #   rp ------ r1 -------- r2
+    #              \
+    #               --------- r3
+    # r1 -> .1
+    # r2 -> .2
+    # rp -> .3
+    # r3 -> .4
+    # loopback network is 10.254.0.X/32
+    #
+    # r1 <- sw1 -> r2
+    # r1-eth0 <-> r2-eth0
+    # 10.0.20.0/24
+    sw = tgen.add_switch("sw1")
+    sw.add_link(tgen.gears["r1"])
+    sw.add_link(tgen.gears["r2"])
+
+    # r1 <- sw2 -> rp
+    # r1-eth1 <-> rp-eth0
+    # 10.0.30.0/24
+    sw = tgen.add_switch("sw2")
+    sw.add_link(tgen.gears["r1"])
+    sw.add_link(tgen.gears["rp"])
+
+    # 10.0.40.0/24
+    sw = tgen.add_switch("sw3")
+    sw.add_link(tgen.gears["r1"])
+    sw.add_link(tgen.gears["r3"])
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(PIMTopo, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     # For all registered routers, load the zebra configuration file
diff --git a/tests/topotests/pim_basic_topo2/test_pim_basic_topo2.py b/tests/topotests/pim_basic_topo2/test_pim_basic_topo2.py
index 2bed11c54..2352a9ab1 100644
--- a/tests/topotests/pim_basic_topo2/test_pim_basic_topo2.py
+++ b/tests/topotests/pim_basic_topo2/test_pim_basic_topo2.py
@@ -48,33 +48,29 @@ from lib.micronet_compat import Topo
 pytestmark = [pytest.mark.bfdd, pytest.mark.pimd]
 
 
-class PimBasicTopo2(Topo):
-    "Test topology builder"
+def build_topo(tgen):
+    "Build function"
 
-    def build(self, *_args, **_opts):
-        "Build function"
-        tgen = get_topogen(self)
+    # Create 4 routers
+    for routern in range(1, 5):
+        tgen.add_router("r{}".format(routern))
 
-        # Create 4 routers
-        for routern in range(1, 5):
-            tgen.add_router("r{}".format(routern))
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
 
-        switch = tgen.add_switch("s1")
-        switch.add_link(tgen.gears["r1"])
-        switch.add_link(tgen.gears["r2"])
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
 
-        switch = tgen.add_switch("s2")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r3"])
-
-        switch = tgen.add_switch("s3")
-        switch.add_link(tgen.gears["r2"])
-        switch.add_link(tgen.gears["r4"])
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r4"])
 
 
 def setup_module(mod):
     "Sets up the pytest environment"
-    tgen = Topogen(PimBasicTopo2, mod.__name__)
+    tgen = Topogen(build_topo, mod.__name__)
     tgen.start_topology()
 
     router_list = tgen.routers()
diff --git a/tests/topotests/rip_topo1/test_rip_topo1.py b/tests/topotests/rip_topo1/test_rip_topo1.py
index 91b4278cd..8cf96777b 100644
--- a/tests/topotests/rip_topo1/test_rip_topo1.py
+++ b/tests/topotests/rip_topo1/test_rip_topo1.py
@@ -38,8 +38,7 @@ from functools import partial
 
 sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 from lib import topotest
-from lib.micronet_compat import Topo
-from lib.micronet_compat import Mininet
+from lib.topogen import Topogen, get_topogen
 
 fatal_error = ""
 
@@ -52,47 +51,38 @@ pytestmark = [pytest.mark.ripd]
 #####################################################
 
 
-class NetworkTopo(Topo):
-    "RIP Topology 1"
-
-    def build(self, **_opts):
-
-        # Setup Routers
-        router = {}
-        #
-        # Setup Main Router
-        router[1] = topotest.addRouter(self, "r1")
-        #
-        # Setup RIP Routers
-        for i in range(2, 4):
-            router[i] = topotest.addRouter(self, "r%s" % i)
-        #
-        # Setup Switches
-        switch = {}
-        #
-        # On main router
-        # First switch is for a dummy interface (for local network)
-        switch[1] = self.addSwitch("sw1")
-        self.addLink(switch[1], router[1], intfName2="r1-eth0")
-        #
-        # Switches for RIP
-        # switch 2 switch is for connection to RIP router
-        switch[2] = self.addSwitch("sw2")
-        self.addLink(switch[2], router[1], intfName2="r1-eth1")
-        self.addLink(switch[2], router[2], intfName2="r2-eth0")
-        # switch 3 is between RIP routers
-        switch[3] = self.addSwitch("sw3")
-        self.addLink(switch[3], router[2], intfName2="r2-eth1")
-        self.addLink(switch[3], router[3], intfName2="r3-eth1")
-        # switch 4 is stub on remote RIP router
-        switch[4] = self.addSwitch("sw4")
-        self.addLink(switch[4], router[3], intfName2="r3-eth0")
-
-        switch[5] = self.addSwitch("sw5")
-        self.addLink(switch[5], router[1], intfName2="r1-eth2")
-
-        switch[6] = self.addSwitch("sw6")
-        self.addLink(switch[6], router[1], intfName2="r1-eth3")
+def build_topo(tgen):
+    # Setup RIP Routers
+    for i in range(1, 4):
+        tgen.add_router("r%s" % i)
+
+    #
+    # On main router
+    # First switch is for a dummy interface (for local network)
+    switch = tgen.add_switch("sw1")
+    switch.add_link(tgen.gears["r1"])
+    #
+    # Switches for RIP
+
+    # switch 2 switch is for connection to RIP router
+    switch = tgen.add_switch("sw2")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
+
+    # switch 3 is between RIP routers
+    switch = tgen.add_switch("sw3")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"], nodeif="r3-eth1")
+
+    # switch 4 is stub on remote RIP router
+    switch = tgen.add_switch("sw4")
+    switch.add_link(tgen.gears["r3"], nodeif="r3-eth0")
+
+    switch = tgen.add_switch("sw5")
+    switch.add_link(tgen.gears["r1"])
+
+    switch = tgen.add_switch("sw6")
+    switch.add_link(tgen.gears["r1"])
 
 
 #####################################################
@@ -103,44 +93,36 @@ class NetworkTopo(Topo):
 
 
 def setup_module(module):
-    global topo, net
-
     print("\n\n** %s: Setup Topology" % module.__name__)
     print("******************************************\n")
 
-    print("Cleanup old Mininet runs")
-    os.system("sudo mn -c > /dev/null 2>&1")
-
     thisDir = os.path.dirname(os.path.realpath(__file__))
-    topo = NetworkTopo()
+    tgen = Topogen(build_topo, module.__name__)
+    tgen.start_topology()
 
-    net = Mininet(controller=None, topo=topo)
-    net.start()
+    net = tgen.net
 
     # Starting Routers
     #
     for i in range(1, 4):
         net["r%s" % i].loadConf("zebra", "%s/r%s/zebra.conf" % (thisDir, i))
         net["r%s" % i].loadConf("ripd", "%s/r%s/ripd.conf" % (thisDir, i))
-        net["r%s" % i].startRouter()
+        tgen.gears["r%s" % i].start()
 
     # For debugging after starting FRR daemons, uncomment the next line
     # CLI(net)
 
 
 def teardown_module(module):
-    global net
-
     print("\n\n** %s: Shutdown Topology" % module.__name__)
     print("******************************************\n")
-
-    # End - Shutdown network
-    net.stop()
+    tgen = get_topogen()
+    tgen.stop_topology()
 
 
 def test_router_running():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -160,7 +142,7 @@ def test_router_running():
 
 def test_converge_protocols():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -172,7 +154,7 @@ def test_converge_protocols():
     print("******************************************\n")
 
     # Not really implemented yet - just sleep 11 secs for now
-    sleep(11)
+    sleep(21)
 
     # Make sure that all daemons are still running
     for i in range(1, 4):
@@ -185,7 +167,7 @@ def test_converge_protocols():
 
 def test_rip_status():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -246,7 +228,7 @@ def test_rip_status():
 
 def test_rip_routes():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -301,7 +283,7 @@ def test_rip_routes():
 
 def test_zebra_ipv4_routingTable():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -367,7 +349,7 @@ def test_zebra_ipv4_routingTable():
 
 def test_shutdown_check_stderr():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
diff --git a/tests/topotests/ripng_topo1/test_ripng_topo1.py b/tests/topotests/ripng_topo1/test_ripng_topo1.py
index 9b3f66111..e2be3abcc 100644
--- a/tests/topotests/ripng_topo1/test_ripng_topo1.py
+++ b/tests/topotests/ripng_topo1/test_ripng_topo1.py
@@ -38,8 +38,7 @@ from functools import partial
 
 sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 from lib import topotest
-from lib.micronet_compat import Topo
-from lib.micronet_compat import Mininet
+from lib.topogen import Topogen, get_topogen
 
 fatal_error = ""
 
@@ -52,46 +51,34 @@ pytestmark = [pytest.mark.ripd]
 #####################################################
 
 
-class NetworkTopo(Topo):
-    "RIPng Topology 1"
-
-    def build(self, **_opts):
-
-        # Setup Routers
-        router = {}
-        #
-        # Setup Main Router
-        router[1] = topotest.addRouter(self, "r1")
-        #
-        # Setup RIPng Routers
-        for i in range(2, 4):
-            router[i] = topotest.addRouter(self, "r%s" % i)
-
-        # Setup Switches
-        switch = {}
-        #
-        # On main router
-        # First switch is for a dummy interface (for local network)
-        switch[1] = self.addSwitch("sw1")
-        self.addLink(switch[1], router[1], intfName2="r1-eth0")
-        #
-        # Switches for RIPng
-        # switch 2 switch is for connection to RIP router
-        switch[2] = self.addSwitch("sw2")
-        self.addLink(switch[2], router[1], intfName2="r1-eth1")
-        self.addLink(switch[2], router[2], intfName2="r2-eth0")
-        # switch 3 is between RIP routers
-        switch[3] = self.addSwitch("sw3")
-        self.addLink(switch[3], router[2], intfName2="r2-eth1")
-        self.addLink(switch[3], router[3], intfName2="r3-eth1")
-        # switch 4 is stub on remote RIP router
-        switch[4] = self.addSwitch("sw4")
-        self.addLink(switch[4], router[3], intfName2="r3-eth0")
-
-        switch[5] = self.addSwitch("sw5")
-        self.addLink(switch[5], router[1], intfName2="r1-eth2")
-        switch[6] = self.addSwitch("sw6")
-        self.addLink(switch[6], router[1], intfName2="r1-eth3")
+def build_topo(tgen):
+    # Setup RIPng Routers
+    for i in range(1, 4):
+        tgen.add_router("r%s" % i)
+
+    #
+    # On main router
+    # First switch is for a dummy interface (for local network)
+    switch = tgen.add_switch("sw1")
+    switch.add_link(tgen.gears["r1"])
+    #
+    # Switches for RIPng
+    # switch 2 switch is for connection to RIP router
+    switch = tgen.add_switch("sw2")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
+    # switch 3 is between RIP routers
+    switch = tgen.add_switch("sw3")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"], nodeif="r3-eth1")
+    # switch 4 is stub on remote RIP router
+    switch = tgen.add_switch("sw4")
+    switch.add_link(tgen.gears["r3"], nodeif="r3-eth0")
+
+    switch = tgen.add_switch("sw5")
+    switch.add_link(tgen.gears["r1"])
+    switch = tgen.add_switch("sw6")
+    switch.add_link(tgen.gears["r1"])
 
 
 #####################################################
@@ -102,44 +89,36 @@ class NetworkTopo(Topo):
 
 
 def setup_module(module):
-    global topo, net
-
     print("\n\n** %s: Setup Topology" % module.__name__)
     print("******************************************\n")
 
-    print("Cleanup old Mininet runs")
-    os.system("sudo mn -c > /dev/null 2>&1")
-
     thisDir = os.path.dirname(os.path.realpath(__file__))
-    topo = NetworkTopo()
+    tgen = Topogen(build_topo, module.__name__)
+    tgen.start_topology()
 
-    net = Mininet(controller=None, topo=topo)
-    net.start()
+    net = tgen.net
 
     # Starting Routers
     #
     for i in range(1, 4):
         net["r%s" % i].loadConf("zebra", "%s/r%s/zebra.conf" % (thisDir, i))
         net["r%s" % i].loadConf("ripngd", "%s/r%s/ripngd.conf" % (thisDir, i))
-        net["r%s" % i].startRouter()
+        tgen.gears["r%s" % i].start()
 
     # For debugging after starting FRR daemons, uncomment the next line
     # CLI(net)
 
 
 def teardown_module(module):
-    global net
-
     print("\n\n** %s: Shutdown Topology" % module.__name__)
     print("******************************************\n")
-
-    # End - Shutdown network
-    net.stop()
+    tgen = get_topogen()
+    tgen.stop_topology()
 
 
 def test_router_running():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -159,7 +138,7 @@ def test_router_running():
 
 def test_converge_protocols():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -184,7 +163,7 @@ def test_converge_protocols():
 
 def test_ripng_status():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -252,7 +231,7 @@ def test_ripng_status():
 
 def test_ripng_routes():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -319,7 +298,7 @@ def test_ripng_routes():
 
 def test_zebra_ipv6_routingTable():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -387,7 +366,7 @@ def test_zebra_ipv6_routingTable():
 
 def test_shutdown_check_stderr():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
@@ -416,7 +395,7 @@ def test_shutdown_check_stderr():
 
 def test_shutdown_check_memleak():
     global fatal_error
-    global net
+    net = get_topogen().net
 
     # Skip if previous fatal error condition is raised
     if fatal_error != "":
diff --git a/tests/topotests/static_routing_with_ebgp/test_static_routes_topo1_ebgp.py b/tests/topotests/static_routing_with_ebgp/test_static_routes_topo1_ebgp.py
index 7b9b61fd9..3298be17e 100644
--- a/tests/topotests/static_routing_with_ebgp/test_static_routes_topo1_ebgp.py
+++ b/tests/topotests/static_routing_with_ebgp/test_static_routes_topo1_ebgp.py
@@ -68,14 +68,6 @@ from lib.topojson import build_topo_from_json, build_config_from_json
 
 pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
 
-# Reading the data from JSON File for topology creation
-JSONFILE = "{}/static_routes_topo1_ebgp.json".format(CWD)
-try:
-    with open(JSONFILE, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(JSONFILE)
-
 # Global variables
 ADDR_TYPES = check_address_types()
 NETWORK = {"ipv4": ["11.0.20.1/32", "11.0.20.2/32"], "ipv6": ["2::1/128", "2::2/128"]}
@@ -84,25 +76,6 @@ NETWORK2 = {"ipv4": "11.0.20.1/32", "ipv6": "2::1/128"}
 PREFIX1 = {"ipv4": "110.0.20.1/32", "ipv6": "20::1/128"}
 
 
-class CreateTopo(Topo):
-    """
-    Test CreateTopo - topology 1.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-    def dumdum(self):
-        """ Dummy """
-        print("%s", self.name)
-
-
 def setup_module(mod):
     """
     Sets up the pytest environment.
@@ -117,7 +90,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/static_routes_topo1_ebgp.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/static_routing_with_ebgp/test_static_routes_topo2_ebgp.py b/tests/topotests/static_routing_with_ebgp/test_static_routes_topo2_ebgp.py
index c0edfef5d..8c98a88bd 100644
--- a/tests/topotests/static_routing_with_ebgp/test_static_routes_topo2_ebgp.py
+++ b/tests/topotests/static_routing_with_ebgp/test_static_routes_topo2_ebgp.py
@@ -75,13 +75,6 @@ from lib.topojson import build_topo_from_json, build_config_from_json
 
 pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/static_routes_topo2_ebgp.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 # Global variables
 BGP_CONVERGENCE = False
 ADDR_TYPES = check_address_types()
@@ -123,21 +116,6 @@ topo_diag = """
 """
 
 
-class CreateTopo(Topo):
-    """
-    Test CreateTopo - topology 1.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
 
@@ -145,7 +123,6 @@ def setup_module(mod):
 
     * `mod`: module name
     """
-    global topo
     testsuite_run_time = time.asctime(time.localtime(time.time()))
     logger.info("Testsuite start time: {}".format(testsuite_run_time))
     logger.info("=" * 40)
@@ -153,7 +130,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/static_routes_topo2_ebgp.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/static_routing_with_ebgp/test_static_routes_topo3_ebgp.py b/tests/topotests/static_routing_with_ebgp/test_static_routes_topo3_ebgp.py
index f088fd618..703e295e5 100644
--- a/tests/topotests/static_routing_with_ebgp/test_static_routes_topo3_ebgp.py
+++ b/tests/topotests/static_routing_with_ebgp/test_static_routes_topo3_ebgp.py
@@ -70,14 +70,6 @@ from lib.topojson import build_topo_from_json, build_config_from_json
 
 pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/static_routes_topo3_ebgp.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
-
 # Global variables
 BGP_CONVERGENCE = False
 ADDR_TYPES = check_address_types()
@@ -108,21 +100,6 @@ NETWORK2 = {"ipv4": ["11.0.20.1/32"], "ipv6": ["2::1/128"]}
 NEXT_HOP_IP = []
 
 
-class CreateTopo(Topo):
-    """
-    Test CreateTopo - topology 1.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
 
@@ -130,7 +107,6 @@ def setup_module(mod):
 
     * `mod`: module name
     """
-    global topo
     testsuite_run_time = time.asctime(time.localtime(time.time()))
     logger.info("Testsuite start time: {}".format(testsuite_run_time))
     logger.info("=" * 40)
@@ -138,7 +114,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/static_routes_topo3_ebgp.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/static_routing_with_ebgp/test_static_routes_topo4_ebgp.py b/tests/topotests/static_routing_with_ebgp/test_static_routes_topo4_ebgp.py
index 217f8467d..bc85a752a 100644
--- a/tests/topotests/static_routing_with_ebgp/test_static_routes_topo4_ebgp.py
+++ b/tests/topotests/static_routing_with_ebgp/test_static_routes_topo4_ebgp.py
@@ -72,16 +72,8 @@ from lib.bgp import (
 )
 from lib.topojson import build_topo_from_json, build_config_from_json
 
-pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
-
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/static_routes_topo4_ebgp.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
+pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
 
 # Global variables
 BGP_CONVERGENCE = False
@@ -92,21 +84,6 @@ NEXT_HOP_IP = {}
 pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
 
 
-class CreateTopo(Topo):
-    """
-    Test CreateTopo - topology 1.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Set up the pytest environment.
@@ -120,7 +97,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/static_routes_topo4_ebgp.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/static_routing_with_ibgp/test_static_routes_topo1_ibgp.py b/tests/topotests/static_routing_with_ibgp/test_static_routes_topo1_ibgp.py
index ea888c137..b571e312d 100644
--- a/tests/topotests/static_routing_with_ibgp/test_static_routes_topo1_ibgp.py
+++ b/tests/topotests/static_routing_with_ibgp/test_static_routes_topo1_ibgp.py
@@ -68,14 +68,6 @@ from lib.topojson import build_topo_from_json, build_config_from_json
 
 pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/static_routes_topo1_ibgp.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
-
 # Global variables
 BGP_CONVERGENCE = False
 ADDR_TYPES = check_address_types()
@@ -85,21 +77,6 @@ NETWORK2 = {"ipv4": "11.0.20.1/32", "ipv6": "2::1/128"}
 PREFIX1 = {"ipv4": "110.0.20.1/32", "ipv6": "20::1/128"}
 
 
-class CreateTopo(Topo):
-    """
-    Test CreateTopo - topology 1.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
 
@@ -107,7 +84,6 @@ def setup_module(mod):
 
     * `mod`: module name
     """
-    global topo
     testsuite_run_time = time.asctime(time.localtime(time.time()))
     logger.info("Testsuite start time: {}".format(testsuite_run_time))
     logger.info("=" * 40)
@@ -115,7 +91,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/static_routes_topo1_ibgp.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/static_routing_with_ibgp/test_static_routes_topo2_ibgp.py b/tests/topotests/static_routing_with_ibgp/test_static_routes_topo2_ibgp.py
index b58543cc9..20697bf19 100644
--- a/tests/topotests/static_routing_with_ibgp/test_static_routes_topo2_ibgp.py
+++ b/tests/topotests/static_routing_with_ibgp/test_static_routes_topo2_ibgp.py
@@ -77,13 +77,6 @@ from lib.topotest import version_cmp
 
 pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/static_routes_topo2_ibgp.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 # Global variables
 BGP_CONVERGENCE = False
 ADDR_TYPES = check_address_types()
@@ -125,21 +118,6 @@ topo_diag = """
 """
 
 
-class CreateTopo(Topo):
-    """
-    Test CreateTopo - topology 1.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
 
@@ -147,7 +125,6 @@ def setup_module(mod):
 
     * `mod`: module name
     """
-    global topo
     testsuite_run_time = time.asctime(time.localtime(time.time()))
     logger.info("Testsuite start time: {}".format(testsuite_run_time))
     logger.info("=" * 40)
@@ -155,7 +132,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/static_routes_topo2_ibgp.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/static_routing_with_ibgp/test_static_routes_topo3_ibgp.py b/tests/topotests/static_routing_with_ibgp/test_static_routes_topo3_ibgp.py
index 8e769ea66..ac7a80745 100644
--- a/tests/topotests/static_routing_with_ibgp/test_static_routes_topo3_ibgp.py
+++ b/tests/topotests/static_routing_with_ibgp/test_static_routes_topo3_ibgp.py
@@ -71,14 +71,6 @@ from lib.topojson import build_topo_from_json, build_config_from_json
 
 pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/static_routes_topo3_ibgp.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
-
 # Global variables
 BGP_CONVERGENCE = False
 ADDR_TYPES = check_address_types()
@@ -109,21 +101,6 @@ NETWORK2 = {"ipv4": ["11.0.20.1/32"], "ipv6": ["2::1/128"]}
 NEXT_HOP_IP = []
 
 
-class CreateTopo(Topo):
-    """
-    Test CreateTopo - topology 1.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
 
@@ -131,7 +108,6 @@ def setup_module(mod):
 
     * `mod`: module name
     """
-    global topo
     testsuite_run_time = time.asctime(time.localtime(time.time()))
     logger.info("Testsuite start time: {}".format(testsuite_run_time))
     logger.info("=" * 40)
@@ -139,7 +115,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/static_routes_topo3_ibgp.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers
diff --git a/tests/topotests/static_routing_with_ibgp/test_static_routes_topo4_ibgp.py b/tests/topotests/static_routing_with_ibgp/test_static_routes_topo4_ibgp.py
index eb828ea03..8dcdc8093 100644
--- a/tests/topotests/static_routing_with_ibgp/test_static_routes_topo4_ibgp.py
+++ b/tests/topotests/static_routing_with_ibgp/test_static_routes_topo4_ibgp.py
@@ -70,13 +70,6 @@ from lib.bgp import (
 from lib.topojson import build_topo_from_json, build_config_from_json
 from lib.topotest import version_cmp
 
-# Reading the data from JSON File for topology creation
-jsonFile = "{}/static_routes_topo4_ibgp.json".format(CWD)
-try:
-    with open(jsonFile, "r") as topoJson:
-        topo = json.load(topoJson)
-except IOError:
-    assert False, "Could not read file {}".format(jsonFile)
 
 # Global variables
 BGP_CONVERGENCE = False
@@ -87,27 +80,11 @@ NEXT_HOP_IP = {}
 pytestmark = [pytest.mark.bgpd, pytest.mark.staticd]
 
 
-class CreateTopo(Topo):
-    """
-    Test CreateTopo - topology 1.
-
-    * `Topo`: Topology object
-    """
-
-    def build(self, *_args, **_opts):
-        """Build function."""
-        tgen = get_topogen(self)
-
-        # Building topology from json file
-        build_topo_from_json(tgen, topo)
-
-
 def setup_module(mod):
     """
     Set up the pytest environment.
     * `mod`: module name
     """
-    global topo
     testsuite_run_time = time.asctime(time.localtime(time.time()))
     logger.info("Testsuite start time: {}".format(testsuite_run_time))
     logger.info("=" * 40)
@@ -115,7 +92,10 @@ def setup_module(mod):
     logger.info("Running setup_module to create topology")
 
     # This function initiates the topology build with Topogen...
-    tgen = Topogen(CreateTopo, mod.__name__)
+    json_file = "{}/static_routes_topo4_ibgp.json".format(CWD)
+    tgen = Topogen(json_file, mod.__name__)
+    global topo
+    topo = tgen.json_topo
     # ... and here it calls Mininet initialization functions.
 
     # Starting topology, create tmp files which are loaded to routers