Merge pull request #12366 from manojvn/ospfv2-flood-reduction

ospfd: Support OSPF Refresh and Flooding Reduction RFC4136.

16 files changed, 2769 insertions, 129 deletions

diff --git a/lib/log.h b/lib/log.h
index 8e94d3fd8..b8452ac21 100644
--- a/lib/log.h
+++ b/lib/log.h
@@ -114,6 +114,21 @@ extern int proto_redistnum(int afi, const char *s);
 
 extern const char *zserv_command_string(unsigned int command);
 
+#define OSPF_LOG(level, cond, fmt, ...)                                        \
+	do {                                                                   \
+		if (cond)                                                      \
+			zlog_##level(fmt, ##__VA_ARGS__);                      \
+	} while (0)
+
+#define OSPF_LOG_ERR(fmt, ...) OSPF_LOG(err, true, fmt, ##__VA_ARGS__)
+
+#define OSPF_LOG_WARN(fmt, ...) OSPF_LOG(warn, true, fmt, ##__VA_ARGS__)
+
+#define OSPF_LOG_INFO(fmt, ...) OSPF_LOG(info, true, fmt, ##__VA_ARGS__)
+
+#define OSPF_LOG_DEBUG(cond, fmt, ...) OSPF_LOG(debug, cond, fmt, ##__VA_ARGS__)
+
+#define OSPF_LOG_NOTICE(fmt, ...) OSPF_LOG(notice, true, fmt, ##__VA_ARGS__)
 
 /* structure useful for avoiding repeated rendering of the same timestamp */
 struct timestamp_control {
diff --git a/ospfd/ospf_abr.c b/ospfd/ospf_abr.c
index 55cb8b183..8f177cbce 100644
--- a/ospfd/ospf_abr.c
+++ b/ospfd/ospf_abr.c
@@ -1559,6 +1559,254 @@ static void ospf_abr_announce_stub_defaults(struct ospf *ospf)
 		zlog_debug("%s: Stop", __func__);
 }
 
+/** @brief Function to check and generate indication
+ *	   LSA for area on which we received
+ *	   indication LSA flush.
+ *  @param Ospf instance.
+ *  @param Area on which indication lsa flush is to be generated.
+ *  @return Void.
+ */
+void ospf_generate_indication_lsa(struct ospf *ospf, struct ospf_area *area)
+{
+	bool area_fr_not_supp = false;
+
+	/* Check if you have any area which doesn't support
+	 * flood reduction.
+	 */
+
+	area_fr_not_supp = ospf_check_fr_enabled_all(ospf) ? false : true;
+
+	/* If any one of the area doestn't support FR, generate
+	 * indication LSA on behalf of that area.
+	 */
+
+	if (area_fr_not_supp && !area->fr_info.area_ind_lsa_recvd &&
+	    !area->fr_info.indication_lsa_self &&
+	    !area->fr_info.area_dc_clear) {
+
+		struct prefix_ipv4 p;
+		struct ospf_lsa *new;
+
+		p.family = AF_INET;
+		p.prefix = ospf->router_id;
+		p.prefixlen = IPV4_MAX_BITLEN;
+
+		new = ospf_summary_asbr_lsa_originate(&p, OSPF_LS_INFINITY,
+						      area);
+		if (!new) {
+			zlog_debug("%s: Indication lsa originate failed",
+				   __func__);
+			return;
+		}
+		/* save the indication lsa for that area */
+		area->fr_info.indication_lsa_self = new;
+	}
+}
+
+/** @brief Function to receive and process indication LSA
+ *	   flush from area.
+ *  @param lsa being flushed.
+ *  @return Void.
+ */
+void ospf_recv_indication_lsa_flush(struct ospf_lsa *lsa)
+{
+	if (!IS_LSA_SELF(lsa) && IS_LSA_MAXAGE(lsa) &&
+	    ospf_check_indication_lsa(lsa)) {
+		lsa->area->fr_info.area_ind_lsa_recvd = false;
+
+		OSPF_LOG_INFO("%s: Received an ind lsa: %pI4 area %pI4",
+			      __func__, &lsa->data->id, &lsa->area->area_id);
+
+		if (!IS_OSPF_ABR(lsa->area->ospf))
+			return;
+
+		/* If the LSA received is a indication LSA with maxage on
+		 * the network, then check and regenerate indication
+		 * LSA if any of our areas don't support flood reduction.
+		 */
+		ospf_generate_indication_lsa(lsa->area->ospf, lsa->area);
+	}
+}
+
+/** @brief Function to generate indication LSAs.
+ *  @param Ospf instance.
+ *  @param Area on behalf of which indication
+ *	   LSA is generated LSA.
+ *  @return Void.
+ */
+void ospf_abr_generate_indication_lsa(struct ospf *ospf,
+				      const struct ospf_area *area)
+{
+	struct ospf_lsa *new;
+	struct listnode *node;
+	struct ospf_area *o_area;
+
+	for (ALL_LIST_ELEMENTS_RO(ospf->areas, node, o_area)) {
+		if (o_area == area)
+			continue;
+
+		if (o_area->fr_info.indication_lsa_self ||
+		    o_area->fr_info.area_ind_lsa_recvd ||
+		    o_area->fr_info.area_dc_clear) {
+			/* if the area has already received an
+			 * indication LSA or if area already has
+			 * LSAs with DC bit 0 other than
+			 * indication LSA then don't generate
+			 * indication LSA in those areas.
+			 */
+			OSPF_LOG_DEBUG(IS_DEBUG_OSPF_EVENT,
+				       "Area %pI4 has LSAs with dc bit clear",
+				       &o_area->area_id);
+			continue;
+
+		} else {
+
+			struct prefix_ipv4 p;
+
+			p.family = AF_INET;
+			p.prefix = ospf->router_id;
+			p.prefixlen = IPV4_MAX_BITLEN;
+
+			new = ospf_summary_asbr_lsa_originate(
+				&p, OSPF_LS_INFINITY, o_area);
+			if (!new) {
+				zlog_debug(
+					"%s: Indication lsa originate Failed",
+					__func__);
+				return;
+			}
+			/* save the indication lsa for that area */
+			o_area->fr_info.indication_lsa_self = new;
+		}
+	}
+}
+
+/** @brief Flush the indication LSA from all the areas
+ *	   of ospf instance.
+ *  @param Ospf instance.
+ *  @return Void.
+ */
+void ospf_flush_indication_lsas(struct ospf *ospf)
+{
+	struct ospf_area *area;
+	struct listnode *node;
+
+	for (ALL_LIST_ELEMENTS_RO(ospf->areas, node, area)) {
+		if (area->fr_info.indication_lsa_self) {
+			OSPF_LOG_INFO(
+				"Flushing ind lsa: %pI4 area %pI4",
+				&area->fr_info.indication_lsa_self->data->id,
+				&area->area_id);
+			ospf_schedule_lsa_flush_area(
+				area, area->fr_info.indication_lsa_self);
+			area->fr_info.indication_lsa_self = NULL;
+		}
+	}
+}
+
+/** @brief Check if flood reduction is enabled on
+ *	   all the areas.
+ *  @param Ospf instance.
+ *  @return Void.
+ */
+bool ospf_check_fr_enabled_all(struct ospf *ospf)
+{
+	const struct ospf_area *area;
+	struct listnode *node;
+
+	for (ALL_LIST_ELEMENTS_RO(ospf->areas, node, area))
+		if (!ospf_check_area_fr_enabled(area))
+			return false;
+
+	return true;
+}
+
+/** @brief Abr function to check conditions for generation
+ *	   of indication. LSAs/announcing non-DNA routers
+ *	   in the area.
+ *  @param thread
+ *  @return 0.
+ */
+static void ospf_abr_announce_non_dna_routers(struct thread *thread)
+{
+	struct ospf_area *area;
+	struct listnode *node;
+	struct ospf *ospf = THREAD_ARG(thread);
+
+	THREAD_OFF(ospf->t_abr_fr);
+
+	if (!IS_OSPF_ABR(ospf))
+		return;
+
+	OSPF_LOG_DEBUG(IS_DEBUG_OSPF_EVENT, "%s(): Start", __func__);
+
+	for (ALL_LIST_ELEMENTS_RO(ospf->areas, node, area)) {
+		OSPF_LOG_DEBUG(IS_DEBUG_OSPF_EVENT,
+			       "%s: Area %pI4 FR enabled: %d", __func__,
+			       &area->area_id, area->fr_info.enabled);
+		OSPF_LOG_DEBUG(
+			IS_DEBUG_OSPF_EVENT,
+			"LSA with DC bit clear: %d Recived indication LSA: %d",
+			area->fr_info.area_dc_clear,
+			area->fr_info.area_ind_lsa_recvd);
+		OSPF_LOG_DEBUG(IS_DEBUG_OSPF_EVENT, "FR state change: %d",
+			       area->fr_info.state_changed);
+		if (!OSPF_IS_AREA_BACKBONE(area) &&
+		    area->fr_info.area_dc_clear) {
+			/* rfc4136 rfc1793: Suppose if the abr is connected to
+			 * a regular non-backbone OSPF area, Furthermore if
+			 * the area has LSAs with the DC-bit clear, other
+			 * than indication-LSAs. Then originate indication-LSAs
+			 * into all other directly-connected "regular" areas,
+			 * including the backbone area.
+			 */
+			ospf_abr_generate_indication_lsa(ospf, area);
+		}
+
+		if (OSPF_IS_AREA_BACKBONE(area) &&
+		    (area->fr_info.area_dc_clear ||
+		     area->fr_info.area_ind_lsa_recvd)) {
+			/* rfc4136 rfc1793: Suppose if the abr is connected to
+			 * backbone OSPF area. Furthermore, if backbone has
+			 * LSAs with the DC-bit clear that are either
+			 * a) not indication-LSAs or indication-LSAs or
+			 * b) indication-LSAs that have been originated by
+			 *    other routers,
+			 * then originate indication-LSAs into all other
+			 * directly-connected "regular" non-backbone areas.
+			 */
+			ospf_abr_generate_indication_lsa(ospf, area);
+		}
+
+		if (area->fr_info.enabled && area->fr_info.state_changed &&
+		    area->fr_info.indication_lsa_self) {
+			/* Ospf area flood reduction state changed
+			 * area now supports flood reduction.
+			 * check if all other areas support flood reduction
+			 * if yes then flush indication LSAs generated in
+			 * all the areas.
+			 */
+			if (ospf_check_fr_enabled_all(ospf))
+				ospf_flush_indication_lsas(ospf);
+
+			area->fr_info.state_changed = false;
+		}
+
+		/* If previously we had generated indication lsa
+		 * but now area has lsas with dc bit set to 0
+		 * apart from indication lsa, we'll clear indication lsa
+		 */
+		if (area->fr_info.area_dc_clear &&
+		    area->fr_info.indication_lsa_self) {
+			ospf_schedule_lsa_flush_area(
+				area, area->fr_info.indication_lsa_self);
+			area->fr_info.indication_lsa_self = NULL;
+		}
+	}
+
+	OSPF_LOG_DEBUG(IS_DEBUG_OSPF_EVENT, "%s(): Stop", __func__);
+}
+
 static int ospf_abr_remove_unapproved_translates_apply(struct ospf *ospf,
 						       struct ospf_lsa *lsa)
 {
@@ -1613,9 +1861,13 @@ static void ospf_abr_remove_unapproved_summaries(struct ospf *ospf)
 					ospf_lsa_flush_area(lsa, area);
 
 		LSDB_LOOP (ASBR_SUMMARY_LSDB(area), rn, lsa)
-			if (ospf_lsa_is_self_originated(ospf, lsa))
-				if (!CHECK_FLAG(lsa->flags, OSPF_LSA_APPROVED))
-					ospf_lsa_flush_area(lsa, area);
+			if (ospf_lsa_is_self_originated(ospf, lsa) &&
+			    !CHECK_FLAG(lsa->flags, OSPF_LSA_APPROVED) &&
+			    /* Do not remove indication LSAs while
+			     * flushing unapproved summaries.
+			     */
+			    !ospf_check_indication_lsa(lsa))
+				ospf_lsa_flush_area(lsa, area);
 	}
 
 	if (IS_DEBUG_OSPF_EVENT)
@@ -1778,6 +2030,20 @@ void ospf_abr_task(struct ospf *ospf)
 		if (IS_DEBUG_OSPF_EVENT)
 			zlog_debug("%s: announce stub defaults", __func__);
 		ospf_abr_announce_stub_defaults(ospf);
+
+		if (ospf->fr_configured) {
+			OSPF_LOG_DEBUG(IS_DEBUG_OSPF_EVENT,
+				       "%s(): announce non-DNArouters",
+				       __func__);
+			/*
+			 * Schedule indication lsa generation timer,
+			 * giving time for route synchronization in
+			 * all the routers.
+			 */
+			thread_add_timer(
+				master, ospf_abr_announce_non_dna_routers, ospf,
+				OSPF_ABR_DNA_TIMER, &ospf->t_abr_fr);
+		}
 	}
 
 	if (IS_DEBUG_OSPF_EVENT)
diff --git a/ospfd/ospf_abr.h b/ospfd/ospf_abr.h
index 21e87669f..19d444b12 100644
--- a/ospfd/ospf_abr.h
+++ b/ospfd/ospf_abr.h
@@ -8,6 +8,11 @@
 #define _ZEBRA_OSPF_ABR_H
 
 #define OSPF_ABR_TASK_DELAY 	5
+#define OSPF_ABR_DNA_TIMER 10
+/* Delay in announceing Non-DNA routers
+ * so that LSAs are completely synced
+ * before generating indication LSAs.
+ */
 
 #define OSPF_AREA_RANGE_ADVERTISE	(1 << 0)
 #define OSPF_AREA_RANGE_SUBSTITUTE	(1 << 1)
@@ -69,4 +74,20 @@ extern void ospf_schedule_abr_task(struct ospf *);
 extern void ospf_abr_announce_network_to_area(struct prefix_ipv4 *, uint32_t,
 					      struct ospf_area *);
 extern void ospf_abr_nssa_check_status(struct ospf *ospf);
+extern void ospf_abr_generate_indication_lsa(struct ospf *ospf,
+					     const struct ospf_area *area);
+extern void ospf_flush_indication_lsas(struct ospf *ospf);
+extern void ospf_generate_indication_lsa(struct ospf *ospf,
+					 struct ospf_area *area);
+extern bool ospf_check_fr_enabled_all(struct ospf *ospf);
+extern void ospf_recv_indication_lsa_flush(struct ospf_lsa *lsa);
+
+/** @brief Static inline functions.
+ *  @param Area pointer.
+ *  @return area Flood Reduction status.
+ */
+static inline bool ospf_check_area_fr_enabled(const struct ospf_area *area)
+{
+	return area->fr_info.enabled ? true : false;
+}
 #endif /* _ZEBRA_OSPF_ABR_H */
diff --git a/ospfd/ospf_flood.c b/ospfd/ospf_flood.c
index debbcd964..d0453bbc4 100644
--- a/ospfd/ospf_flood.c
+++ b/ospfd/ospf_flood.c
@@ -35,6 +35,75 @@
 
 extern struct zclient *zclient;
 
+/** @brief Function to refresh type-5 and type-7 DNA
+ *	   LSAs when we receive an indication LSA.
+ *  @param Ospf instance.
+ *  @return Void.
+ */
+void ospf_refresh_dna_type5_and_type7_lsas(struct ospf *ospf)
+{
+	struct route_node *rn;
+	struct ospf_lsa *lsa = NULL;
+
+	LSDB_LOOP (EXTERNAL_LSDB(ospf), rn, lsa)
+		if (IS_LSA_SELF(lsa) &&
+		    CHECK_FLAG(lsa->data->ls_age, DO_NOT_AGE))
+			ospf_lsa_refresh(ospf, lsa);
+
+	LSDB_LOOP (NSSA_LSDB(ospf), rn, lsa)
+		if (IS_LSA_SELF(lsa) &&
+		    CHECK_FLAG(lsa->data->ls_age, DO_NOT_AGE))
+			ospf_lsa_refresh(ospf, lsa);
+}
+
+/** @brief Function to update area flood reduction states.
+ *  @param area pointer.
+ *  @return Void.
+ */
+void ospf_area_update_fr_state(struct ospf_area *area)
+{
+	unsigned int count_router_lsas = 0;
+
+	if (area == NULL)
+		return;
+
+	count_router_lsas =
+		(unsigned int)(ospf_lsdb_count(area->lsdb, OSPF_ROUTER_LSA) -
+			       ospf_lsdb_count_self(area->lsdb,
+						    OSPF_ROUTER_LSA));
+
+	if (count_router_lsas >
+	    (unsigned int)area->fr_info.router_lsas_recv_dc_bit) {
+		area->fr_info.enabled = false;
+		area->fr_info.area_dc_clear = true;
+		return;
+	} else if (count_router_lsas <
+		   (unsigned int)area->fr_info.router_lsas_recv_dc_bit) {
+		/* This can never happen, total number of router lsas received
+		 * can never be less than router lsas received with dc bit set
+		 */
+		OSPF_LOG_ERR("%s: Counter mismatch for area %pI4", __func__,
+			     &area->area_id);
+		OSPF_LOG_ERR(
+			"%s: router LSAs in lsdb %d router LSAs recvd with dc bit set %d",
+			__func__, count_router_lsas,
+			area->fr_info.router_lsas_recv_dc_bit);
+		return;
+	}
+
+	area->fr_info.area_dc_clear = false;
+
+	if (OSPF_FR_CONFIG(area->ospf, area)) {
+		if (!area->fr_info.enabled) {
+			area->fr_info.enabled = true;
+			area->fr_info.state_changed = true;
+		}
+	} else {
+		area->fr_info.enabled = false;
+		area->fr_info.area_dc_clear = true;
+	}
+}
+
 /* Do the LSA acking specified in table 19, Section 13.5, row 2
  * This get called from ospf_flood_out_interface. Declared inline
  * for speed. */
@@ -413,6 +482,55 @@ int ospf_flood(struct ospf *ospf, struct ospf_neighbor *nbr,
 	if (!(new = ospf_lsa_install(ospf, oi, new)))
 		return -1; /* unknown LSA type or any other error condition */
 
+	/* check if the installed LSA is an indication LSA */
+	if (ospf_check_indication_lsa(new) && !IS_LSA_SELF(new) &&
+	    !IS_LSA_MAXAGE(new)) {
+		new->area->fr_info.area_ind_lsa_recvd = true;
+		/* check if there are already type 5 LSAs originated
+		 * with DNA bit set, if yes reoriginate those LSAs.
+		 */
+		ospf_refresh_dna_type5_and_type7_lsas(ospf);
+	}
+
+	/* Check if we recived an indication LSA flush on backbone
+	 * network.
+	 */
+	ospf_recv_indication_lsa_flush(new);
+
+	if (new->area && OSPF_FR_CONFIG(ospf, new->area)) {
+		struct lsa_header const *lsah = new->data;
+
+		if (!CHECK_FLAG(lsah->options, OSPF_OPTION_DC) &&
+		    !ospf_check_indication_lsa(new)) {
+
+			new->area->fr_info.area_dc_clear = true;
+			/* check of previously area supported flood reduction */
+			if (new->area->fr_info.enabled) {
+				new->area->fr_info.enabled = false;
+				OSPF_LOG_DEBUG(
+					IS_DEBUG_OSPF_EVENT,
+					"Flood Reduction STATE on -> off by %s LSA",
+					dump_lsa_key(new));
+				/* if yes update all the lsa to the area the
+				 * new LSAs will have DNA bit set to 0.
+				 */
+				ospf_refresh_area_self_lsas(new->area);
+			}
+		} else if (!new->area->fr_info.enabled) {
+			/* check again after installing new LSA that area
+			 * supports flood reduction.
+			 */
+			ospf_area_update_fr_state(new->area);
+			if (new->area->fr_info.enabled) {
+				OSPF_LOG_DEBUG(
+					IS_DEBUG_OSPF_EVENT,
+					"Flood Reduction STATE off -> on by %s LSA",
+					dump_lsa_key(new));
+				ospf_refresh_area_self_lsas(new->area);
+			}
+		}
+	}
+
 	/* Acknowledge the receipt of the LSA by sending a Link State
 	   Acknowledgment packet back out the receiving interface. */
 	if (lsa_ack_flag)
@@ -450,6 +568,25 @@ int ospf_flood_through_interface(struct ospf_interface *oi,
 	if (!ospf_if_is_enable(oi))
 		return 0;
 
+	/* If flood reduction is configured, set the DC bit on the lsa. */
+	if (IS_LSA_SELF(lsa)) {
+		if (OSPF_FR_CONFIG(oi->area->ospf, oi->area)) {
+			if (!ospf_check_indication_lsa(lsa)) {
+				SET_FLAG(lsa->data->options, OSPF_OPTION_DC);
+				ospf_lsa_checksum(lsa->data);
+			}
+		} else if (CHECK_FLAG(lsa->data->options, OSPF_OPTION_DC)) {
+			UNSET_FLAG(lsa->data->options, OSPF_OPTION_DC);
+			ospf_lsa_checksum(lsa->data);
+		}
+
+		/* If flood reduction is enabled then set DNA bit on the
+		 * self lsas.
+		 */
+		if (oi->area->fr_info.enabled)
+			SET_FLAG(lsa->data->ls_age, DO_NOT_AGE);
+	}
+
 	/* Remember if new LSA is added to a retransmit list. */
 	retx_flag = 0;
 
diff --git a/ospfd/ospf_flood.h b/ospfd/ospf_flood.h
index 6dce6937b..3757400d0 100644
--- a/ospfd/ospf_flood.h
+++ b/ospfd/ospf_flood.h
@@ -53,5 +53,7 @@ extern struct external_info *ospf_external_info_check(struct ospf *,
 						      struct ospf_lsa *);
 
 extern void ospf_lsdb_init(struct ospf_lsdb *);
+extern void ospf_area_update_fr_state(struct ospf_area *area);
+extern void ospf_refresh_dna_type5_and_type7_lsas(struct ospf *ospf);
 
 #endif /* _ZEBRA_OSPF_FLOOD_H */
diff --git a/ospfd/ospf_lsa.c b/ospfd/ospf_lsa.c
index ffbfc2af2..49e342d72 100644
--- a/ospfd/ospf_lsa.c
+++ b/ospfd/ospf_lsa.c
@@ -70,6 +70,16 @@ uint32_t get_metric(uint8_t *metric)
 	return m;
 }
 
+/** @brief The Function checks self generated DoNotAge.
+ *  @param lsa pointer.
+ *  @return true or false.
+ */
+bool ospf_check_dna_lsa(const struct ospf_lsa *lsa)
+{
+	return ((IS_LSA_SELF(lsa) && CHECK_FLAG(lsa->data->ls_age, DO_NOT_AGE))
+			? true
+			: false);
+}
 
 struct timeval int2tv(int a)
 {
@@ -121,6 +131,16 @@ int get_age(struct ospf_lsa *lsa)
 {
 	struct timeval rel;
 
+	/* As per rfc4136, the self-originated LSAs in their
+	 * own database keep aging, however rfc doesn't tell
+	 * till how long the LSA should be aged, as of now
+	 * we are capping it for OSPF_LSA_MAXAGE.
+	 */
+
+	/* If LSA is marked as donotage */
+	if (CHECK_FLAG(lsa->data->ls_age, DO_NOT_AGE) && !IS_LSA_SELF(lsa))
+		return ntohs(lsa->data->ls_age);
+
 	monotime_since(&lsa->tv_recv, &rel);
 	return ntohs(lsa->data->ls_age) + rel.tv_sec;
 }
@@ -1119,6 +1139,10 @@ static struct ospf_lsa *ospf_network_lsa_refresh(struct ospf_lsa *lsa)
 		}
 		return NULL;
 	}
+
+	if (oi->state != ISM_DR)
+		return NULL;
+
 	/* Delete LSA from neighbor retransmit-list. */
 	ospf_ls_retransmit_delete_nbr_area(area, lsa);
 
@@ -1518,10 +1542,15 @@ static struct ospf_lsa *ospf_summary_asbr_lsa_refresh(struct ospf *ospf,
 	struct ospf_lsa *new;
 	struct summary_lsa *sl;
 	struct prefix p;
+	bool ind_lsa = false;
 
 	/* Sanity check. */
 	assert(lsa->data);
 
+	if (lsa->area->fr_info.indication_lsa_self &&
+	    (lsa->area->fr_info.indication_lsa_self == lsa))
+		ind_lsa = true;
+
 	sl = (struct summary_lsa *)lsa->data;
 	p.prefixlen = ip_masklen(sl->mask);
 	new = ospf_summary_asbr_lsa_new(lsa->area, &p, GET_METRIC(sl->metric),
@@ -1536,6 +1565,9 @@ static struct ospf_lsa *ospf_summary_asbr_lsa_refresh(struct ospf *ospf,
 	/* Flood LSA through area. */
 	ospf_flood_through_area(new->area, NULL, new);
 
+	if (ind_lsa)
+		new->area->fr_info.indication_lsa_self = new;
+
 	if (IS_DEBUG_OSPF(lsa, LSA_GENERATE)) {
 		zlog_debug("LSA[Type%d:%pI4]: summary-ASBR-LSA refresh",
 			   new->data->type, &new->data->id);
@@ -3626,6 +3658,49 @@ void ospf_flush_self_originated_lsas_now(struct ospf *ospf)
 	return;
 }
 
+/** @brief Function to refresh all the self originated
+ *	   LSAs for area, when FR state change happens.
+ *  @param area pointer.
+ *  @return Void.
+ */
+void ospf_refresh_area_self_lsas(struct ospf_area *area)
+{
+	struct listnode *node2;
+	struct listnode *nnode2;
+	struct ospf_interface *oi;
+	struct route_node *rn;
+	struct ospf_lsa *lsa;
+
+	if (!area)
+		return;
+
+	if (area->router_lsa_self)
+		ospf_lsa_refresh(area->ospf, area->router_lsa_self);
+
+	for (ALL_LIST_ELEMENTS(area->oiflist, node2, nnode2, oi))
+		if (oi->network_lsa_self)
+			ospf_lsa_refresh(oi->ospf, oi->network_lsa_self);
+
+	LSDB_LOOP (SUMMARY_LSDB(area), rn, lsa)
+		if (IS_LSA_SELF(lsa))
+			ospf_lsa_refresh(area->ospf, lsa);
+	LSDB_LOOP (ASBR_SUMMARY_LSDB(area), rn, lsa)
+		if (IS_LSA_SELF(lsa))
+			ospf_lsa_refresh(area->ospf, lsa);
+	LSDB_LOOP (OPAQUE_LINK_LSDB(area), rn, lsa)
+		if (IS_LSA_SELF(lsa))
+			ospf_lsa_refresh(area->ospf, lsa);
+	LSDB_LOOP (OPAQUE_AREA_LSDB(area), rn, lsa)
+		if (IS_LSA_SELF(lsa))
+			ospf_lsa_refresh(area->ospf, lsa);
+	LSDB_LOOP (EXTERNAL_LSDB(area->ospf), rn, lsa)
+		if (IS_LSA_SELF(lsa))
+			ospf_lsa_refresh(area->ospf, lsa);
+	LSDB_LOOP (OPAQUE_AS_LSDB(area->ospf), rn, lsa)
+		if (IS_LSA_SELF(lsa))
+			ospf_lsa_refresh(area->ospf, lsa);
+}
+
 /* If there is self-originated LSA, then return 1, otherwise return 0. */
 /* An interface-independent version of ospf_lsa_is_self_originated */
 int ospf_lsa_is_self_originated(struct ospf *ospf, struct ospf_lsa *lsa)
@@ -3961,6 +4036,7 @@ void ospf_lsa_refresh_walker(struct thread *t)
 	struct ospf_lsa *lsa;
 	int i;
 	struct list *lsa_to_refresh = list_new();
+	bool dna_lsa;
 
 	if (IS_DEBUG_OSPF(lsa, LSA_REFRESH))
 		zlog_debug("LSA[Refresh]: %s: start", __func__);
@@ -4019,10 +4095,14 @@ void ospf_lsa_refresh_walker(struct thread *t)
 	ospf->lsa_refresher_started = monotime(NULL);
 
 	for (ALL_LIST_ELEMENTS(lsa_to_refresh, node, nnode, lsa)) {
-		ospf_lsa_refresh(ospf, lsa);
-		assert(lsa->lock > 0);
-		ospf_lsa_unlock(
-			&lsa); /* lsa_refresh_queue & temp for lsa_to_refresh*/
+		dna_lsa = ospf_check_dna_lsa(lsa);
+		if (!dna_lsa) { /* refresh only non-DNA LSAs */
+			ospf_lsa_refresh(ospf, lsa);
+			assert(lsa->lock > 0);
+			ospf_lsa_unlock(&lsa); /* lsa_refresh_queue & temp for
+						* lsa_to_refresh.
+						*/
+		}
 	}
 
 	list_delete(&lsa_to_refresh);
diff --git a/ospfd/ospf_lsa.h b/ospfd/ospf_lsa.h
index 6fa6399a9..3c7ea3fda 100644
--- a/ospfd/ospf_lsa.h
+++ b/ospfd/ospf_lsa.h
@@ -45,6 +45,7 @@
 /* OSPF LSA header. */
 struct lsa_header {
 	uint16_t ls_age;
+#define DO_NOT_AGE 0x8000
 	uint8_t options;
 	uint8_t type;
 	struct in_addr id;
@@ -218,6 +219,9 @@ enum lsid_status { LSID_AVAILABLE = 0, LSID_CHANGE, LSID_NOT_AVAILABLE };
 	 || (type == OSPF_SUMMARY_LSA) || (type == OSPF_ASBR_SUMMARY_LSA)      \
 	 || (type == OSPF_AS_EXTERNAL_LSA) || (type == OSPF_AS_NSSA_LSA))
 
+#define OSPF_FR_CONFIG(o, a)                                                   \
+	(o->fr_configured || ((a != NULL) ? a->fr_info.configured : 0))
+
 /* Prototypes. */
 /* XXX: Eek, time functions, similar are in lib/thread.c */
 extern struct timeval int2tv(int);
@@ -343,4 +347,24 @@ extern void ospf_check_and_gen_init_seq_lsa(struct ospf_interface *oi,
 extern void ospf_flush_lsa_from_area(struct ospf *ospf, struct in_addr area_id,
 				     int type);
 extern void ospf_maxage_lsa_remover(struct thread *thread);
+extern bool ospf_check_dna_lsa(const struct ospf_lsa *lsa);
+extern void ospf_refresh_area_self_lsas(struct ospf_area *area);
+
+/** @brief Check if the LSA is an indication LSA.
+ *  @param lsa pointer.
+ *  @return true or false based on lsa info.
+ */
+static inline bool ospf_check_indication_lsa(struct ospf_lsa *lsa)
+{
+	struct summary_lsa *sl = NULL;
+
+	if (lsa->data->type == OSPF_ASBR_SUMMARY_LSA) {
+		sl = (struct summary_lsa *)lsa->data;
+		if ((GET_METRIC(sl->metric) == OSPF_LS_INFINITY) &&
+		    !CHECK_FLAG(lsa->data->options, OSPF_OPTION_DC))
+			return true;
+	}
+
+	return false;
+}
 #endif /* _ZEBRA_OSPF_LSA_H */
diff --git a/ospfd/ospf_lsdb.c b/ospfd/ospf_lsdb.c
index 0d18e9f77..0111c4924 100644
--- a/ospfd/ospf_lsdb.c
+++ b/ospfd/ospf_lsdb.c
@@ -77,6 +77,21 @@ static void ospf_lsdb_delete_entry(struct ospf_lsdb *lsdb,
 	lsdb->type[lsa->data->type].count--;
 	lsdb->type[lsa->data->type].checksum -= ntohs(lsa->data->checksum);
 	lsdb->total--;
+
+	/* Decrement number of router LSAs received with DC bit set */
+	if (lsa->area && (lsa->area->lsdb == lsdb) && !IS_LSA_SELF(lsa) &&
+	    (lsa->data->type == OSPF_ROUTER_LSA) &&
+	    CHECK_FLAG(lsa->data->options, OSPF_OPTION_DC))
+		lsa->area->fr_info.router_lsas_recv_dc_bit--;
+
+	/*
+	 * If the LSA being deleted is indication LSA, then set the
+	 * pointer to NULL.
+	 */
+	if (lsa->area && lsa->area->fr_info.indication_lsa_self &&
+	    (lsa->area->fr_info.indication_lsa_self == lsa))
+		lsa->area->fr_info.indication_lsa_self = NULL;
+
 	rn->info = NULL;
 	route_unlock_node(rn);
 #ifdef MONITOR_LSDB_CHANGE
@@ -113,6 +128,12 @@ void ospf_lsdb_add(struct ospf_lsdb *lsdb, struct ospf_lsa *lsa)
 	lsdb->type[lsa->data->type].count++;
 	lsdb->total++;
 
+	/* Increment number of router LSAs received with DC bit set */
+	if (lsa->area && (lsa->area->lsdb == lsdb) && !IS_LSA_SELF(lsa) &&
+	    (lsa->data->type == OSPF_ROUTER_LSA) &&
+	    CHECK_FLAG(lsa->data->options, OSPF_OPTION_DC))
+		lsa->area->fr_info.router_lsas_recv_dc_bit++;
+
 #ifdef MONITOR_LSDB_CHANGE
 	if (lsdb->new_lsa_hook != NULL)
 		(*lsdb->new_lsa_hook)(lsa);
diff --git a/ospfd/ospf_packet.c b/ospfd/ospf_packet.c
index 4c2f5d72b..5268c9896 100644
--- a/ospfd/ospf_packet.c
+++ b/ospfd/ospf_packet.c
@@ -28,6 +28,7 @@
 #include "ospfd/ospf_network.h"
 #include "ospfd/ospf_interface.h"
 #include "ospfd/ospf_ism.h"
+#include "ospfd/ospf_abr.h"
 #include "ospfd/ospf_asbr.h"
 #include "ospfd/ospf_lsa.h"
 #include "ospfd/ospf_lsdb.h"
@@ -3317,6 +3318,14 @@ static int ospf_make_hello(struct ospf_interface *oi, struct stream *s)
 	else
 		stream_putw(s, 0); /* hello-interval of 0 for fast-hellos */
 
+	/* Check if flood-reduction is enabled,
+	 * if yes set the DC bit in the options.
+	 */
+	if (OSPF_FR_CONFIG(oi->ospf, oi->area))
+		SET_FLAG(OPTIONS(oi), OSPF_OPTION_DC);
+	else if (CHECK_FLAG(OPTIONS(oi), OSPF_OPTION_DC))
+		UNSET_FLAG(OPTIONS(oi), OSPF_OPTION_DC);
+
 	if (IS_DEBUG_OSPF_EVENT)
 		zlog_debug("%s: options: %x, int: %s", __func__, OPTIONS(oi),
 			   IF_NAME(oi));
@@ -3405,6 +3414,8 @@ static int ospf_make_db_desc(struct ospf_interface *oi,
 	options = OPTIONS(oi);
 	if (CHECK_FLAG(oi->ospf->config, OSPF_OPAQUE_CAPABLE))
 		SET_FLAG(options, OSPF_OPTION_O);
+	if (OSPF_FR_CONFIG(oi->ospf, oi->area))
+		SET_FLAG(options, OSPF_OPTION_DC);
 	stream_putc(s, options);
 
 	/* DD flags */
diff --git a/ospfd/ospf_route.c b/ospfd/ospf_route.c
index 25cd32b6f..5f18bff1c 100644
--- a/ospfd/ospf_route.c
+++ b/ospfd/ospf_route.c
@@ -980,6 +980,16 @@ void ospf_prune_unreachable_routers(struct route_table *rtrs)
 						&or->u.std.area_id);
 				}
 
+				/* Unset the DNA flag on lsa, if the router
+				 * which generated this lsa is no longer
+				 * reachabele.
+				 */
+				(CHECK_FLAG(or->u.std.origin->ls_age,
+					    DO_NOT_AGE))
+					? UNSET_FLAG(or->u.std.origin->ls_age,
+						     DO_NOT_AGE)
+					: 0;
+
 				listnode_delete(paths, or);
 				ospf_route_free(or);
 			}
diff --git a/ospfd/ospf_vty.c b/ospfd/ospf_vty.c
index b3e543d22..29bddb119 100644
--- a/ospfd/ospf_vty.c
+++ b/ospfd/ospf_vty.c
@@ -3038,6 +3038,43 @@ static void show_ip_ospf_area(struct vty *vty, struct ospf_area *area,
 			ospf_lsdb_checksum(area->lsdb, OSPF_OPAQUE_AREA_LSA));
 	}
 
+	if (area->fr_info.configured) {
+		if (use_json)
+			json_object_string_add(json_area, "areaFloodReduction",
+					       "configured");
+		else
+			vty_out(vty, "   Flood Reduction is configured.\n");
+	}
+
+	if (area->fr_info.enabled) {
+		if (use_json) {
+			json_object_boolean_true_add(
+				json_area, "areaFloodReductionEnabled");
+			if (area->fr_info.router_lsas_recv_dc_bit)
+				json_object_boolean_true_add(
+					json_area, "lsasRecvDCbitSet");
+			if (area->fr_info.area_ind_lsa_recvd)
+				json_object_string_add(json_area,
+						       "areaIndicationLsaRecv",
+						       "received");
+			if (area->fr_info.indication_lsa_self)
+				json_object_string_addf(
+					json_area, "areaIndicationLsa", "%pI4",
+					&area->fr_info.indication_lsa_self->data
+						 ->id);
+		} else {
+			vty_out(vty, "   Flood Reduction is enabled.\n");
+			vty_out(vty, "   No of LSAs rcv'd with DC bit set %d\n",
+				area->fr_info.router_lsas_recv_dc_bit);
+			if (area->fr_info.area_ind_lsa_recvd)
+				vty_out(vty, "   Ind LSA by other abr.\n");
+			if (area->fr_info.indication_lsa_self)
+				vty_out(vty, "   Ind LSA generated %pI4\n",
+					&area->fr_info.indication_lsa_self->data
+						 ->id);
+		}
+	}
+
 	if (use_json)
 		json_object_object_add(json_areas,
 				       inet_ntop(AF_INET, &area->area_id,
@@ -3273,6 +3310,14 @@ static int show_ip_ospf_common(struct vty *vty, struct ospf *ospf,
 					   : ZEBRA_OSPF_DISTANCE_DEFAULT);
 	}
 
+	if (ospf->fr_configured) {
+		if (json)
+			json_object_string_add(json_vrf, "floodReduction",
+					       "configured");
+		else
+			vty_out(vty, " Flood Reduction is configured.\n");
+	}
+
 	/* Show ABR/ASBR flags. */
 	if (CHECK_FLAG(ospf->flags, OSPF_FLAG_ABR)) {
 		if (json)
@@ -5949,118 +5994,109 @@ static int show_lsa_summary(struct vty *vty, struct ospf_lsa *lsa, int self,
 	struct as_external_lsa *asel;
 	struct prefix_ipv4 p;
 
-	if (lsa != NULL) {
-		/* If self option is set, check LSA self flag. */
-		if (self == 0 || IS_LSA_SELF(lsa)) {
+	if (lsa == NULL)
+		return 0;
 
-			if (!json_lsa) {
-				/* LSA common part show. */
-				vty_out(vty, "%-15pI4",
-					&lsa->data->id);
-				vty_out(vty, "%-15pI4 %4d 0x%08lx 0x%04x",
-					&lsa->data->adv_router,	LS_AGE(lsa),
-					(unsigned long)ntohl(
-						lsa->data->ls_seqnum),
-					ntohs(lsa->data->checksum));
-			} else {
-				char seqnum[10];
-				char checksum[10];
-
-				snprintf(seqnum, sizeof(seqnum), "%x",
-					 ntohl(lsa->data->ls_seqnum));
-				snprintf(checksum, sizeof(checksum), "%x",
-					 ntohs(lsa->data->checksum));
-				json_object_string_addf(json_lsa, "lsId",
-							"%pI4", &lsa->data->id);
-				json_object_string_addf(
-					json_lsa, "advertisedRouter", "%pI4",
-					&lsa->data->adv_router);
-				json_object_int_add(json_lsa, "lsaAge",
-						    LS_AGE(lsa));
-				json_object_string_add(
-					json_lsa, "sequenceNumber", seqnum);
-				json_object_string_add(json_lsa, "checksum",
-						       checksum);
-			}
+	/* If self option is set, check LSA self flag. */
+	if (self == 0 || IS_LSA_SELF(lsa)) {
 
-			/* LSA specific part show. */
-			switch (lsa->data->type) {
-			case OSPF_ROUTER_LSA:
-				rl = (struct router_lsa *)lsa->data;
+		if (!json_lsa) {
+			/* LSA common part show. */
+			vty_out(vty, "%-15pI4", &lsa->data->id);
+			vty_out(vty, "%-15pI4 %4d 0x%08lx 0x%04x",
+				&lsa->data->adv_router, LS_AGE(lsa),
+				(unsigned long)ntohl(lsa->data->ls_seqnum),
+				ntohs(lsa->data->checksum));
+		} else {
+			char seqnum[10];
+			char checksum[10];
+
+			snprintf(seqnum, sizeof(seqnum), "%x",
+				 ntohl(lsa->data->ls_seqnum));
+			snprintf(checksum, sizeof(checksum), "%x",
+				 ntohs(lsa->data->checksum));
+			json_object_string_addf(json_lsa, "lsId", "%pI4",
+						&lsa->data->id);
+			json_object_string_addf(json_lsa, "advertisedRouter",
+						"%pI4", &lsa->data->adv_router);
+			json_object_int_add(json_lsa, "lsaAge", LS_AGE(lsa));
+			json_object_string_add(json_lsa, "sequenceNumber",
+					       seqnum);
+			json_object_string_add(json_lsa, "checksum", checksum);
+		}
+
+		/* LSA specific part show. */
+		switch (lsa->data->type) {
+		case OSPF_ROUTER_LSA:
+			rl = (struct router_lsa *)lsa->data;
 
-				if (!json_lsa)
-					vty_out(vty, " %-d", ntohs(rl->links));
-				else
-					json_object_int_add(json_lsa,
-							    "numOfRouterLinks",
-							    ntohs(rl->links));
-				break;
-			case OSPF_SUMMARY_LSA:
-				sl = (struct summary_lsa *)lsa->data;
+			if (!json_lsa)
+				vty_out(vty, " %-d", ntohs(rl->links));
+			else
+				json_object_int_add(json_lsa,
+						    "numOfRouterLinks",
+						    ntohs(rl->links));
+			break;
+		case OSPF_SUMMARY_LSA:
+			sl = (struct summary_lsa *)lsa->data;
 
-				p.family = AF_INET;
-				p.prefix = sl->header.id;
-				p.prefixlen = ip_masklen(sl->mask);
-				apply_mask_ipv4(&p);
+			p.family = AF_INET;
+			p.prefix = sl->header.id;
+			p.prefixlen = ip_masklen(sl->mask);
+			apply_mask_ipv4(&p);
 
-				if (!json_lsa)
-					vty_out(vty, " %pFX", &p);
-				else {
-					json_object_string_addf(
-						json_lsa, "summaryAddress",
-						"%pFX", &p);
-				}
-				break;
-			case OSPF_AS_EXTERNAL_LSA:
-			case OSPF_AS_NSSA_LSA:
-				asel = (struct as_external_lsa *)lsa->data;
-
-				p.family = AF_INET;
-				p.prefix = asel->header.id;
-				p.prefixlen = ip_masklen(asel->mask);
-				apply_mask_ipv4(&p);
-
-				if (!json_lsa)
-					vty_out(vty, " %s %pFX [0x%lx]",
-						IS_EXTERNAL_METRIC(
-							asel->e[0].tos)
-							? "E2"
-							: "E1",
-						&p,
-						(unsigned long)ntohl(
-							asel->e[0].route_tag));
-				else {
-					json_object_string_add(
-						json_lsa, "metricType",
-						IS_EXTERNAL_METRIC(
-							asel->e[0].tos)
-							? "E2"
-							: "E1");
-					json_object_string_addf(
-						json_lsa, "route", "%pFX", &p);
-					json_object_int_add(
-						json_lsa, "tag",
-						(unsigned long)ntohl(
-							asel->e[0].route_tag));
-				}
-				break;
-			case OSPF_NETWORK_LSA:
-			case OSPF_ASBR_SUMMARY_LSA:
-			case OSPF_OPAQUE_LINK_LSA:
-			case OSPF_OPAQUE_AREA_LSA:
-			case OSPF_OPAQUE_AS_LSA:
-			default:
-				break;
+			if (!json_lsa)
+				vty_out(vty, " %pFX", &p);
+			else {
+				json_object_string_addf(
+					json_lsa, "summaryAddress", "%pFX", &p);
 			}
+			break;
+		case OSPF_AS_EXTERNAL_LSA:
+		case OSPF_AS_NSSA_LSA:
+			asel = (struct as_external_lsa *)lsa->data;
+
+			p.family = AF_INET;
+			p.prefix = asel->header.id;
+			p.prefixlen = ip_masklen(asel->mask);
+			apply_mask_ipv4(&p);
 
 			if (!json_lsa)
-				vty_out(vty, "\n");
+				vty_out(vty, " %s %pFX [0x%lx]",
+					IS_EXTERNAL_METRIC(asel->e[0].tos)
+						? "E2"
+						: "E1",
+					&p,
+					(unsigned long)ntohl(
+						asel->e[0].route_tag));
+			else {
+				json_object_string_add(
+					json_lsa, "metricType",
+					IS_EXTERNAL_METRIC(asel->e[0].tos)
+						? "E2"
+						: "E1");
+				json_object_string_addf(json_lsa, "route",
+							"%pFX", &p);
+				json_object_int_add(
+					json_lsa, "tag",
+					(unsigned long)ntohl(
+						asel->e[0].route_tag));
+			}
+			break;
+		case OSPF_NETWORK_LSA:
+		case OSPF_ASBR_SUMMARY_LSA:
+		case OSPF_OPAQUE_LINK_LSA:
+		case OSPF_OPAQUE_AREA_LSA:
+		case OSPF_OPAQUE_AS_LSA:
+		default:
+			break;
 		}
 
-		return 1;
+		if (!json_lsa)
+			vty_out(vty, "\n");
 	}
 
-	return 0;
+	return 1;
 }
 
 static const char *const show_database_desc[] = {
@@ -6129,7 +6165,16 @@ static void show_ip_ospf_database_header(struct vty *vty, struct ospf_lsa *lsa,
 	struct router_lsa *rlsa = (struct router_lsa *)lsa->data;
 
 	if (!json) {
-		vty_out(vty, "  LS age: %d\n", LS_AGE(lsa));
+		if (IS_LSA_SELF(lsa))
+			vty_out(vty, "  LS age: %d%s\n", LS_AGE(lsa),
+				CHECK_FLAG(lsa->data->ls_age, DO_NOT_AGE)
+					? "(S-DNA)"
+					: "");
+		else
+			vty_out(vty, "  LS age: %d%s\n", LS_AGE(lsa),
+				CHECK_FLAG(lsa->data->ls_age, DO_NOT_AGE)
+					? "(DNA)"
+					: "");
 		vty_out(vty, "  Options: 0x%-2x : %s\n", lsa->data->options,
 			ospf_options_dump(lsa->data->options));
 		vty_out(vty, "  LS Flags: 0x%-2x %s\n", lsa->flags,
@@ -12188,6 +12233,9 @@ static int config_write_ospf_area(struct vty *vty, struct ospf *ospf)
 		if (PREFIX_NAME_OUT(area))
 			vty_out(vty, " area %s filter-list prefix %s out\n",
 				buf, PREFIX_NAME_OUT(area));
+
+		if (area->fr_info.configured)
+			vty_out(vty, " area %s flood-reduction\n", buf);
 	}
 
 	return 0;
@@ -12565,6 +12613,9 @@ static int ospf_config_write_one(struct vty *vty, struct ospf *ospf)
 	if (ospf->lsa_refresh_interval != OSPF_LSA_REFRESH_INTERVAL_DEFAULT)
 		vty_out(vty, " refresh timer %d\n", ospf->lsa_refresh_interval);
 
+	if (ospf->fr_configured)
+		vty_out(vty, " flood-reduction\n");
+
 	/* Redistribute information print. */
 	config_write_ospf_redistribute(vty, ospf);
 
@@ -12947,6 +12998,143 @@ DEFPY_HIDDEN(ospf_maxage_delay_timer, ospf_maxage_delay_timer_cmd,
 	return CMD_SUCCESS;
 }
 
+/*
+ * ------------------------------------------------------------------------*
+ * Following is (vty) configuration functions for flood-reduction handling.
+ * ------------------------------------------------------------------------
+ */
+
+DEFPY(flood_reduction, flood_reduction_cmd, "flood-reduction",
+      "flood reduction feature\n")
+{
+	VTY_DECLVAR_INSTANCE_CONTEXT(ospf, ospf)
+	struct ospf_area *area;
+	struct listnode *node;
+
+	/* Turn on the Flood Reduction feature for the router. */
+	if (!ospf->fr_configured) {
+		ospf->fr_configured = true;
+		OSPF_LOG_DEBUG(IS_DEBUG_OSPF_EVENT,
+			       "Flood Reduction: OFF -> ON");
+		for (ALL_LIST_ELEMENTS_RO(ospf->areas, node, area)) {
+			if (area) {
+				ospf_area_update_fr_state(area);
+				ospf_refresh_area_self_lsas(area);
+			}
+		}
+	}
+
+	return CMD_SUCCESS;
+}
+
+DEFPY(flood_reduction_area, flood_reduction_area_cmd,
+      "area <A.B.C.D|(0-4294967295)> flood-reduction",
+      "OSPF area parameters\n"
+      "OSPF area ID in IP address format\n"
+      "OSPF area ID as a decimal value\n"
+      "Enable flood reduction for area\n")
+{
+	VTY_DECLVAR_INSTANCE_CONTEXT(ospf, ospf)
+	struct ospf_area *oa;
+	int idx = 1;
+	int format;
+	int ret;
+	const char *areaid;
+	struct in_addr area_id;
+
+	areaid = argv[idx]->arg;
+
+	ret = str2area_id(areaid, &area_id, &format);
+	if (ret < 0) {
+		vty_out(vty, "Please specify area by A.B.C.D|<0-4294967295>\n");
+		return CMD_WARNING_CONFIG_FAILED;
+	}
+
+	oa = ospf_area_lookup_by_area_id(ospf, area_id);
+	if (!oa) {
+		vty_out(vty, "OSPF area ID not present\n");
+		return CMD_WARNING_CONFIG_FAILED;
+	}
+
+	/* Turn on the Flood Reduction feature for the area. */
+	if (!oa->fr_info.configured) {
+		oa->fr_info.configured = true;
+		OSPF_LOG_DEBUG(IS_DEBUG_OSPF_EVENT,
+			       "Flood Reduction area %pI4 : OFF -> ON",
+			       &oa->area_id);
+		ospf_area_update_fr_state(oa);
+		ospf_refresh_area_self_lsas(oa);
+	}
+
+	return CMD_SUCCESS;
+}
+
+DEFPY(no_flood_reduction, no_flood_reduction_cmd, "no flood-reduction",
+      NO_STR "flood reduction feature\n")
+{
+	VTY_DECLVAR_INSTANCE_CONTEXT(ospf, ospf)
+	struct listnode *node;
+	struct ospf_area *area;
+
+	/* Turn off the Flood Reduction feature for the router. */
+	if (ospf->fr_configured) {
+		ospf->fr_configured = false;
+		OSPF_LOG_DEBUG(IS_DEBUG_OSPF_EVENT,
+			       "Flood Reduction: ON -> OFF");
+		for (ALL_LIST_ELEMENTS_RO(ospf->areas, node, area)) {
+			if (area) {
+				ospf_area_update_fr_state(area);
+				ospf_refresh_area_self_lsas(area);
+			}
+		}
+	}
+
+	return CMD_SUCCESS;
+}
+
+DEFPY(no_flood_reduction_area, no_flood_reduction_area_cmd,
+      "no area <A.B.C.D|(0-4294967295)> flood-reduction",
+      NO_STR
+      "OSPF area parameters\n"
+      "OSPF area ID in IP address format\n"
+      "OSPF area ID as a decimal value\n"
+      "Disable flood reduction for area\n")
+{
+	VTY_DECLVAR_INSTANCE_CONTEXT(ospf, ospf)
+	struct ospf_area *oa;
+	int idx = 2;
+	int format;
+	int ret;
+	const char *areaid;
+	struct in_addr area_id;
+
+	areaid = argv[idx]->arg;
+
+	ret = str2area_id(areaid, &area_id, &format);
+	if (ret < 0) {
+		vty_out(vty, "Please specify area by A.B.C.D|<0-4294967295>\n");
+		return CMD_WARNING_CONFIG_FAILED;
+	}
+
+	oa = ospf_area_lookup_by_area_id(ospf, area_id);
+	if (!oa) {
+		vty_out(vty, "OSPF area ID not present\n");
+		return CMD_WARNING_CONFIG_FAILED;
+	}
+
+	/* Turn off the Flood Reduction feature for the area. */
+	if (oa->fr_info.configured) {
+		oa->fr_info.configured = false;
+		OSPF_LOG_DEBUG(IS_DEBUG_OSPF_EVENT,
+			       "Flood Reduction area %pI4 : ON -> OFF",
+			       &oa->area_id);
+		ospf_area_update_fr_state(oa);
+		ospf_refresh_area_self_lsas(oa);
+	}
+
+	return CMD_SUCCESS;
+}
+
 void ospf_vty_clear_init(void)
 {
 	install_element(ENABLE_NODE, &clear_ip_ospf_interface_cmd);
@@ -13107,6 +13295,12 @@ void ospf_vty_init(void)
 	install_element(OSPF_NODE, &ospf_lsa_refresh_timer_cmd);
 	install_element(OSPF_NODE, &ospf_maxage_delay_timer_cmd);
 
+	/* Flood Reduction commands */
+	install_element(OSPF_NODE, &flood_reduction_cmd);
+	install_element(OSPF_NODE, &no_flood_reduction_cmd);
+	install_element(OSPF_NODE, &flood_reduction_area_cmd);
+	install_element(OSPF_NODE, &no_flood_reduction_area_cmd);
+
 	/* Init interface related vty commands. */
 	ospf_vty_if_init();
 
diff --git a/ospfd/ospfd.c b/ospfd/ospfd.c
index 1c8ebccea..0296d9d9f 100644
--- a/ospfd/ospfd.c
+++ b/ospfd/ospfd.c
@@ -452,6 +452,8 @@ static struct ospf *ospf_new(unsigned short instance, const char *name)
 	 */
 	ospf_gr_nvm_read(new);
 
+	new->fr_configured = false;
+
 	return new;
 }
 
@@ -802,6 +804,7 @@ static void ospf_finish_final(struct ospf *ospf)
 	THREAD_OFF(ospf->t_maxage);
 	THREAD_OFF(ospf->t_maxage_walker);
 	THREAD_OFF(ospf->t_abr_task);
+	THREAD_OFF(ospf->t_abr_fr);
 	THREAD_OFF(ospf->t_asbr_check);
 	THREAD_OFF(ospf->t_asbr_nssa_redist_update);
 	THREAD_OFF(ospf->t_distribute_update);
@@ -947,6 +950,15 @@ struct ospf_area *ospf_area_new(struct ospf *ospf, struct in_addr area_id)
 	/* Self-originated LSAs initialize. */
 	new->router_lsa_self = NULL;
 
+	/* Initialize FR field */
+	new->fr_info.enabled = false;
+	new->fr_info.configured = false;
+	new->fr_info.state_changed = false;
+	new->fr_info.router_lsas_recv_dc_bit = 0;
+	new->fr_info.indication_lsa_self = NULL;
+	new->fr_info.area_ind_lsa_recvd = false;
+	new->fr_info.area_dc_clear = false;
+
 	ospf_opaque_type10_lsa_init(new);
 
 	new->oiflist = list_new();
diff --git a/ospfd/ospfd.h b/ospfd/ospfd.h
index cb26ef5fb..4df65ea75 100644
--- a/ospfd/ospfd.h
+++ b/ospfd/ospfd.h
@@ -101,7 +101,25 @@ struct ospf_redist {
 		struct route_map *map;
 	} route_map; /* +1 is for default-information */
 #define ROUTEMAP_NAME(R)   (R->route_map.name)
-#define ROUTEMAP(R)        (R->route_map.map)
+#define ROUTEMAP(R) (R->route_map.map)
+};
+
+/* OSPF area flood reduction info */
+struct ospf_area_fr_info {
+	bool enabled;       /* Area support for Flood Reduction */
+	bool configured;    /* Flood Reduction configured per area knob */
+	bool state_changed; /* flood reduction state change info */
+	int router_lsas_recv_dc_bit; /* Number of unique router lsas
+				      * received with DC bit set.
+				      * (excluding self)
+				      */
+	bool area_ind_lsa_recvd;     /* Indication lsa received in this area */
+	bool area_dc_clear;	  /* Area has atleast one lsa with dc bit 0(
+				      * excluding indication lsa)
+				      */
+	struct ospf_lsa *indication_lsa_self; /* Indication LSA generated
+					       * in the area.
+					       */
 };
 
 /* ospf->config */
@@ -240,6 +258,7 @@ struct ospf {
 
 	/* Threads. */
 	struct thread *t_abr_task;	  /* ABR task timer. */
+	struct thread *t_abr_fr;	  /* ABR FR timer. */
 	struct thread *t_asbr_check;	/* ASBR check timer. */
 	struct thread *t_asbr_nssa_redist_update; /* ASBR NSSA redistribution
 						     update timer. */
@@ -391,6 +410,9 @@ struct ospf {
 	bool ti_lfa_enabled;
 	enum protection_type ti_lfa_protection_type;
 
+	/* Flood Reduction configuration state */
+	bool fr_configured;
+
 	QOBJ_FIELDS;
 };
 DECLARE_QOBJ_TYPE(ospf);
@@ -576,6 +598,8 @@ struct ospf_area {
 	uint32_t act_ints;  /* Active interfaces. */
 	uint32_t full_nbrs; /* Fully adjacent neighbors. */
 	uint32_t full_vls;  /* Fully adjacent virtual neighbors. */
+
+	struct ospf_area_fr_info fr_info; /* Flood reduction info. */
 };
 
 /* OSPF config network structure. */
diff --git a/tests/topotests/lib/ospf.py b/tests/topotests/lib/ospf.py
index f1937f45b..7609c7f89 100644
--- a/tests/topotests/lib/ospf.py
+++ b/tests/topotests/lib/ospf.py
@@ -8,6 +8,7 @@
 import ipaddress
 import sys
 from copy import deepcopy
+from time import sleep
 
 # Import common_config to use commomnly used APIs
 from lib.common_config import (
@@ -188,6 +189,24 @@ def __create_ospf_global(tgen, input_dict, router, build, load_config, ospf):
             cmd = "no maximum-paths"
         config_data.append(cmd)
 
+    # Flood reduction.
+    flood_data = ospf_data.setdefault("flood-reduction", {})
+    if flood_data:
+        cmd = "flood-reduction"
+        del_action = ospf_data.setdefault("del_flood_reduction", False)
+        if del_action:
+            cmd = "no flood-reduction"
+        config_data.append(cmd)
+
+    # LSA refresh timer - A hidden command.
+    refresh_data = ospf_data.setdefault("lsa-refresh", {})
+    if refresh_data:
+        cmd = "ospf lsa-refresh {}".format(refresh_data)
+        del_action = ospf_data.setdefault("del_lsa_refresh", False)
+        if del_action:
+            cmd = "no ospf lsa-refresh"
+        config_data.append(cmd)
+
     # redistribute command
     redistribute_data = ospf_data.setdefault("redistribute", {})
     if redistribute_data:
@@ -220,6 +239,9 @@ def __create_ospf_global(tgen, input_dict, router, build, load_config, ospf):
                 if "type" in area:
                     cmd = cmd + " {}".format(area["type"])
 
+                if "flood-reduction" in area:
+                    cmd = cmd + " flood-reduction"
+
                 del_action = area.setdefault("delete", False)
                 if del_action:
                     cmd = "no {}".format(cmd)
@@ -724,9 +746,6 @@ def verify_ospf_neighbor(
     return result
 
 
-################################
-# Verification procs
-################################
 @retry(retry_timeout=50)
 def verify_ospf6_neighbor(tgen, topo=None, dut=None, input_dict=None, lan=False):
     """
@@ -1339,8 +1358,10 @@ def verify_ospf_interface(
     return result
 
 
-@retry(retry_timeout=20)
-def verify_ospf_database(tgen, topo, dut, input_dict, expected=True):
+@retry(retry_timeout=40)
+def verify_ospf_database(
+    tgen, topo, dut, input_dict, vrf=None, lsatype=None, rid=None, expected=True
+):
     """
     This API is to verify ospf lsa's by running
     show ip ospf database command.
@@ -1398,7 +1419,23 @@ def verify_ospf_database(tgen, topo, dut, input_dict, expected=True):
     rnode = tgen.routers()[dut]
 
     logger.info("Verifying OSPF interface on router %s:", dut)
-    show_ospf_json = run_frr_cmd(rnode, "show ip ospf database json", isjson=True)
+
+    if not rid:
+        rid = "self-originate"
+    if lsatype:
+        if vrf is None:
+            command = "show ip ospf database {} {} json".format(lsatype, rid)
+        else:
+            command = "show ip ospf database {} {} vrf {} json".format(
+                lsatype, rid, vrf
+            )
+    else:
+        if vrf is None:
+            command = "show ip ospf database json"
+        else:
+            command = "show ip ospf database vrf {} json".format(vrf)
+
+    show_ospf_json = run_frr_cmd(rnode, command, isjson=True)
     # Verifying output dictionary show_ospf_json is empty or not
     if not bool(show_ospf_json):
         errormsg = "OSPF is not running"
@@ -1407,26 +1444,40 @@ def verify_ospf_database(tgen, topo, dut, input_dict, expected=True):
     # for inter and inter lsa's
     ospf_db_data = input_dict.setdefault("areas", None)
     ospf_external_lsa = input_dict.setdefault("AS External Link States", None)
+    # import pdb; pdb.set_trace()
     if ospf_db_data:
         for ospf_area, area_lsa in ospf_db_data.items():
-            if ospf_area in show_ospf_json["areas"]:
-                if "Router Link States" in area_lsa:
-                    for lsa in area_lsa["Router Link States"]:
+            if ospf_area in show_ospf_json["routerLinkStates"]["areas"]:
+                if "routerLinkStates" in area_lsa:
+                    for lsa in area_lsa["routerLinkStates"]:
+                        _advrtr = lsa.setdefault("advertisedRouter", None)
+                        _options = lsa.setdefault("options", None)
+
                         if (
-                            lsa
-                            in show_ospf_json["areas"][ospf_area]["Router Link States"]
+                            _options
+                            and lsa["lsaId"]
+                            == show_ospf_json["routerLinkStates"]["areas"][ospf_area][
+                                0
+                            ]["linkStateId"]
+                            and lsa["options"]
+                            == show_ospf_json["routerLinkStates"]["areas"][ospf_area][
+                                0
+                            ]["options"]
                         ):
-                            logger.info(
-                                "[DUT: %s]  OSPF LSDB area %s:Router " "LSA %s",
-                                router,
-                                ospf_area,
-                                lsa,
-                            )
                             result = True
+                            break
                         else:
-                            errormsg = (
-                                "[DUT: {}]  OSPF LSDB area {}: expected"
-                                " Router LSA is {}".format(router, ospf_area, lsa)
+                            errormsg = '[DUT: {}]  OSPF LSA options: expected {}, Received Options are {} lsa["options"] {} OSPF LSAID: expected lsaid {}, Received lsaid {}'.format(
+                                dut,
+                                show_ospf_json["routerLinkStates"]["areas"][ospf_area][
+                                    0
+                                ]["options"],
+                                _options,
+                                lsa["options"],
+                                show_ospf_json["routerLinkStates"]["areas"][ospf_area][
+                                    0
+                                ]["linkStateId"],
+                                lsa["lsaId"],
                             )
                             return errormsg
                 if "Net Link States" in area_lsa:
@@ -2476,3 +2527,495 @@ def verify_ospf_gr_helper(tgen, topo, dut, input_dict=None):
 
     logger.debug("Exiting lib API: {}".format(sys._getframe().f_code.co_name))
     return result
+
+
+def get_ospf_database(tgen, topo, dut, input_dict, vrf=None, lsatype=None, rid=None):
+    """
+    This API is to return ospf lsa's by running
+    show ip ospf database command.
+
+    Parameters
+    ----------
+    * `tgen` : Topogen object
+    * `dut`: device under test
+    * `input_dict` : Input dict data, required when configuring from testcase
+    * `topo` : next to be verified
+    * `vrf` : vrf to be checked
+    * `lsatype` : type of lsa to be checked
+    * `rid` : router id for lsa to be checked
+    Usage
+    -----
+    input_dict = {
+        "areas": {
+        "0.0.0.0": {
+            "routerLinkStates": {
+                "100.1.1.0-100.1.1.0": {
+                    "LSID": "100.1.1.0",
+                    "Advertised router": "100.1.1.0",
+                    "LSA Age": 130,
+                    "Sequence Number": "80000006",
+                    "Checksum": "a703",
+                    "Router links": 3
+                }
+            },
+            "networkLinkStates": {
+                "10.0.0.2-100.1.1.1": {
+                    "LSID": "10.0.0.2",
+                    "Advertised router": "100.1.1.1",
+                    "LSA Age": 137,
+                    "Sequence Number": "80000001",
+                    "Checksum": "9583"
+                }
+            },
+        },
+        }
+    }
+    result = get_ospf_database(tgen, topo, dut, input_dict)
+
+    Returns
+    -------
+    True or False (Error Message)
+    """
+
+    result = False
+    router = dut
+    logger.debug("Entering lib API: {}".format(sys._getframe().f_code.co_name))
+    sleep(10)
+    if "ospf" not in topo["routers"][dut]:
+        errormsg = "[DUT: {}] OSPF is not configured on the router.".format(dut)
+        return errormsg
+
+    rnode = tgen.routers()[dut]
+
+    logger.info("Verifying OSPF interface on router %s:", dut)
+    if not rid:
+        rid = "self-originate"
+    if lsatype:
+        if vrf is None:
+            command = "show ip ospf database {} {} json".format(lsatype, rid)
+        else:
+            command = "show ip ospf database {} {} vrf {} json".format(
+                lsatype, rid, vrf
+            )
+    else:
+        if vrf is None:
+            command = "show ip ospf database json"
+        else:
+            command = "show ip ospf database vrf {} json".format(vrf)
+
+    show_ospf_json = run_frr_cmd(rnode, command, isjson=True)
+    # Verifying output dictionary show_ospf_json is empty or not
+    if not bool(show_ospf_json):
+        errormsg = "OSPF is not running"
+        return errormsg
+
+    # for inter and inter lsa's
+    ospf_db_data = input_dict.setdefault("areas", None)
+    ospf_external_lsa = input_dict.setdefault("asExternalLinkStates", None)
+
+    if ospf_db_data:
+        for ospf_area, area_lsa in ospf_db_data.items():
+            if "areas" in show_ospf_json and ospf_area in show_ospf_json["areas"]:
+                if "routerLinkStates" in area_lsa:
+                    for lsa in area_lsa["routerLinkStates"]:
+                        for rtrlsa in show_ospf_json["areas"][ospf_area][
+                            "routerLinkStates"
+                        ]:
+                            _advrtr = lsa.setdefault("advertisedRouter", None)
+                            _options = lsa.setdefault("options", None)
+                            if (
+                                _advrtr
+                                and lsa["lsaId"] == rtrlsa["lsaId"]
+                                and lsa["advertisedRouter"]
+                                == rtrlsa["advertisedRouter"]
+                            ):
+                                result = True
+                                break
+                            if (
+                                _options
+                                and lsa["lsaId"] == rtrlsa["lsaId"]
+                                and lsa["options"] == rtrlsa["options"]
+                            ):
+                                result = True
+                                break
+
+                        if result:
+                            logger.info(
+                                "[DUT: %s]  OSPF LSDB area %s:Router " "LSA %s",
+                                router,
+                                ospf_area,
+                                lsa,
+                            )
+                            break
+                    else:
+                        errormsg = (
+                            "[DUT: {}]  OSPF LSDB area {}: expected"
+                            " Router LSA is {}\n found Router LSA: {}".format(
+                                router, ospf_area, lsa, rtrlsa
+                            )
+                        )
+                        return errormsg
+
+                if "networkLinkStates" in area_lsa:
+                    for lsa in area_lsa["networkLinkStates"]:
+                        for netlsa in show_ospf_json["areas"][ospf_area][
+                            "networkLinkStates"
+                        ]:
+                            if (
+                                lsa
+                                in show_ospf_json["areas"][ospf_area][
+                                    "networkLinkStates"
+                                ]
+                            ):
+                                if (
+                                    lsa["lsaId"] == netlsa["lsaId"]
+                                    and lsa["advertisedRouter"]
+                                    == netlsa["advertisedRouter"]
+                                ):
+                                    result = True
+                                    break
+                        if result:
+                            logger.info(
+                                "[DUT: %s]  OSPF LSDB area %s:Network " "LSA %s",
+                                router,
+                                ospf_area,
+                                lsa,
+                            )
+                            break
+                        else:
+                            errormsg = (
+                                "[DUT: {}]  OSPF LSDB area {}: expected"
+                                " Network LSA is {}".format(router, ospf_area, lsa)
+                            )
+                            return errormsg
+
+                if "summaryLinkStates" in area_lsa:
+                    for lsa in area_lsa["summaryLinkStates"]:
+                        for t3lsa in show_ospf_json["areas"][ospf_area][
+                            "summaryLinkStates"
+                        ]:
+                            if (
+                                lsa["lsaId"] == t3lsa["lsaId"]
+                                and lsa["advertisedRouter"] == t3lsa["advertisedRouter"]
+                            ):
+                                result = True
+                                break
+                        if result:
+                            logger.info(
+                                "[DUT: %s]  OSPF LSDB area %s:Summary " "LSA %s",
+                                router,
+                                ospf_area,
+                                lsa,
+                            )
+                            break
+                        else:
+                            errormsg = (
+                                "[DUT: {}]  OSPF LSDB area {}: expected"
+                                " Summary LSA is {}".format(router, ospf_area, lsa)
+                            )
+                            return errormsg
+
+                if "nssaExternalLinkStates" in area_lsa:
+                    for lsa in area_lsa["nssaExternalLinkStates"]:
+                        for t7lsa in show_ospf_json["areas"][ospf_area][
+                            "nssaExternalLinkStates"
+                        ]:
+                            if (
+                                lsa["lsaId"] == t7lsa["lsaId"]
+                                and lsa["advertisedRouter"] == t7lsa["advertisedRouter"]
+                            ):
+                                result = True
+                                break
+                        if result:
+                            logger.info(
+                                "[DUT: %s]  OSPF LSDB area %s:Type7 " "LSA %s",
+                                router,
+                                ospf_area,
+                                lsa,
+                            )
+                            break
+                        else:
+                            errormsg = (
+                                "[DUT: {}]  OSPF LSDB area {}: expected"
+                                " Type7 LSA is {}".format(router, ospf_area, lsa)
+                            )
+                            return errormsg
+
+                if "asbrSummaryLinkStates" in area_lsa:
+                    for lsa in area_lsa["asbrSummaryLinkStates"]:
+                        for t4lsa in show_ospf_json["areas"][ospf_area][
+                            "asbrSummaryLinkStates"
+                        ]:
+                            if (
+                                lsa["lsaId"] == t4lsa["lsaId"]
+                                and lsa["advertisedRouter"] == t4lsa["advertisedRouter"]
+                            ):
+                                result = True
+                                break
+                        if result:
+                            logger.info(
+                                "[DUT: %s]  OSPF LSDB area %s:ASBR Summary " "LSA %s",
+                                router,
+                                ospf_area,
+                                lsa,
+                            )
+                            result = True
+                        else:
+                            errormsg = (
+                                "[DUT: {}]  OSPF LSDB area {}: expected"
+                                " ASBR Summary LSA is {}".format(router, ospf_area, lsa)
+                            )
+                            return errormsg
+
+                if "linkLocalOpaqueLsa" in area_lsa:
+                    for lsa in area_lsa["linkLocalOpaqueLsa"]:
+                        try:
+                            for lnklsa in show_ospf_json["areas"][ospf_area][
+                                "linkLocalOpaqueLsa"
+                            ]:
+                                if (
+                                    lsa["lsaId"] in lnklsa["lsaId"]
+                                    and "linkLocalOpaqueLsa"
+                                    in show_ospf_json["areas"][ospf_area]
+                                ):
+                                    logger.info(
+                                        (
+                                            "[DUT: FRR]  OSPF LSDB area %s:Opaque-LSA"
+                                            "%s",
+                                            ospf_area,
+                                            lsa,
+                                        )
+                                    )
+                                    result = True
+                                else:
+                                    errormsg = (
+                                        "[DUT: FRR] OSPF LSDB area: {} "
+                                        "expected Opaque-LSA is {}, Found is {}".format(
+                                            ospf_area, lsa, show_ospf_json
+                                        )
+                                    )
+                                    raise ValueError(errormsg)
+                                    return errormsg
+                        except KeyError:
+                            errormsg = "[DUT: FRR] linkLocalOpaqueLsa Not " "present"
+                            return errormsg
+            else:
+                if "routerLinkStates" in area_lsa:
+                    for lsa in area_lsa["routerLinkStates"]:
+                        for rtrlsa in show_ospf_json["routerLinkStates"]:
+                            _advrtr = lsa.setdefault("advertisedRouter", None)
+                            _options = lsa.setdefault("options", None)
+                            _age = lsa.setdefault("lsaAge", None)
+                            if (
+                                _options
+                                and lsa["options"]
+                                == show_ospf_json["routerLinkStates"][rtrlsa][
+                                    ospf_area
+                                ][0]["options"]
+                            ):
+                                result = True
+                                break
+                            if (
+                                _age is not "get"
+                                and lsa["lsaAge"]
+                                == show_ospf_json["routerLinkStates"][rtrlsa][
+                                    ospf_area
+                                ][0]["lsaAge"]
+                            ):
+                                result = True
+                                break
+
+                            if _age == "get":
+                                return "{}".format(
+                                    show_ospf_json["routerLinkStates"][rtrlsa][
+                                        ospf_area
+                                    ][0]["lsaAge"]
+                                )
+                        if result:
+                            logger.info(
+                                "[DUT: %s]  OSPF LSDB area %s:Router " "LSA %s",
+                                router,
+                                ospf_area,
+                                lsa,
+                            )
+                            break
+                    else:
+                        errormsg = (
+                            "[DUT: {}]  OSPF LSDB area {}: expected"
+                            " Router LSA is {}\n found Router LSA: {}".format(
+                                router,
+                                ospf_area,
+                                lsa,
+                                show_ospf_json["routerLinkStates"],
+                            )
+                        )
+                        return errormsg
+
+                if "networkLinkStates" in area_lsa:
+                    for lsa in area_lsa["networkLinkStates"]:
+                        for netlsa in show_ospf_json["areas"][ospf_area][
+                            "networkLinkStates"
+                        ]:
+                            if (
+                                lsa
+                                in show_ospf_json["areas"][ospf_area][
+                                    "networkLinkStates"
+                                ]
+                            ):
+                                if (
+                                    lsa["lsaId"] == netlsa["lsaId"]
+                                    and lsa["advertisedRouter"]
+                                    == netlsa["advertisedRouter"]
+                                ):
+                                    result = True
+                                    break
+                        if result:
+                            logger.info(
+                                "[DUT: %s]  OSPF LSDB area %s:Network " "LSA %s",
+                                router,
+                                ospf_area,
+                                lsa,
+                            )
+                            break
+                        else:
+                            errormsg = (
+                                "[DUT: {}]  OSPF LSDB area {}: expected"
+                                " Network LSA is {}".format(router, ospf_area, lsa)
+                            )
+                            return errormsg
+
+                if "summaryLinkStates" in area_lsa:
+                    for lsa in area_lsa["summaryLinkStates"]:
+                        for t3lsa in show_ospf_json["areas"][ospf_area][
+                            "summaryLinkStates"
+                        ]:
+                            if (
+                                lsa["lsaId"] == t3lsa["lsaId"]
+                                and lsa["advertisedRouter"] == t3lsa["advertisedRouter"]
+                            ):
+                                result = True
+                                break
+                        if result:
+                            logger.info(
+                                "[DUT: %s]  OSPF LSDB area %s:Summary " "LSA %s",
+                                router,
+                                ospf_area,
+                                lsa,
+                            )
+                            break
+                        else:
+                            errormsg = (
+                                "[DUT: {}]  OSPF LSDB area {}: expected"
+                                " Summary LSA is {}".format(router, ospf_area, lsa)
+                            )
+                            return errormsg
+
+                if "nssaExternalLinkStates" in area_lsa:
+                    for lsa in area_lsa["nssaExternalLinkStates"]:
+                        for t7lsa in show_ospf_json["areas"][ospf_area][
+                            "nssaExternalLinkStates"
+                        ]:
+                            if (
+                                lsa["lsaId"] == t7lsa["lsaId"]
+                                and lsa["advertisedRouter"] == t7lsa["advertisedRouter"]
+                            ):
+                                result = True
+                                break
+                        if result:
+                            logger.info(
+                                "[DUT: %s]  OSPF LSDB area %s:Type7 " "LSA %s",
+                                router,
+                                ospf_area,
+                                lsa,
+                            )
+                            break
+                        else:
+                            errormsg = (
+                                "[DUT: {}]  OSPF LSDB area {}: expected"
+                                " Type7 LSA is {}".format(router, ospf_area, lsa)
+                            )
+                            return errormsg
+
+                if "asbrSummaryLinkStates" in area_lsa:
+                    for lsa in area_lsa["asbrSummaryLinkStates"]:
+                        for t4lsa in show_ospf_json["areas"][ospf_area][
+                            "asbrSummaryLinkStates"
+                        ]:
+                            if (
+                                lsa["lsaId"] == t4lsa["lsaId"]
+                                and lsa["advertisedRouter"] == t4lsa["advertisedRouter"]
+                            ):
+                                result = True
+                                break
+                        if result:
+                            logger.info(
+                                "[DUT: %s]  OSPF LSDB area %s:ASBR Summary " "LSA %s",
+                                router,
+                                ospf_area,
+                                lsa,
+                            )
+                            result = True
+                        else:
+                            errormsg = (
+                                "[DUT: {}]  OSPF LSDB area {}: expected"
+                                " ASBR Summary LSA is {}".format(router, ospf_area, lsa)
+                            )
+                            return errormsg
+
+                if "linkLocalOpaqueLsa" in area_lsa:
+                    for lsa in area_lsa["linkLocalOpaqueLsa"]:
+                        try:
+                            for lnklsa in show_ospf_json["areas"][ospf_area][
+                                "linkLocalOpaqueLsa"
+                            ]:
+                                if (
+                                    lsa["lsaId"] in lnklsa["lsaId"]
+                                    and "linkLocalOpaqueLsa"
+                                    in show_ospf_json["areas"][ospf_area]
+                                ):
+                                    logger.info(
+                                        (
+                                            "[DUT: FRR]  OSPF LSDB area %s:Opaque-LSA"
+                                            "%s",
+                                            ospf_area,
+                                            lsa,
+                                        )
+                                    )
+                                    result = True
+                                else:
+                                    errormsg = (
+                                        "[DUT: FRR] OSPF LSDB area: {} "
+                                        "expected Opaque-LSA is {}, Found is {}".format(
+                                            ospf_area, lsa, show_ospf_json
+                                        )
+                                    )
+                                    raise ValueError(errormsg)
+                                    return errormsg
+                        except KeyError:
+                            errormsg = "[DUT: FRR] linkLocalOpaqueLsa Not " "present"
+                            return errormsg
+
+    if ospf_external_lsa:
+        for lsa in ospf_external_lsa:
+            try:
+                for t5lsa in show_ospf_json["asExternalLinkStates"]:
+                    if (
+                        lsa["lsaId"] == t5lsa["lsaId"]
+                        and lsa["advertisedRouter"] == t5lsa["advertisedRouter"]
+                    ):
+                        result = True
+                        break
+            except KeyError:
+                result = False
+            if result:
+                logger.info("[DUT: %s]  OSPF LSDB:External LSA %s", router, lsa)
+                result = True
+            else:
+                errormsg = (
+                    "[DUT: {}]  OSPF LSDB : expected"
+                    " External LSA is {}".format(router, lsa)
+                )
+                return errormsg
+
+    logger.debug("Exiting lib API: {}".format(sys._getframe().f_code.co_name))
+    return result
diff --git a/tests/topotests/ospf_basic_functionality/ospf_flood_reduction.json b/tests/topotests/ospf_basic_functionality/ospf_flood_reduction.json
new file mode 100644
index 000000000..74443cdc7
--- /dev/null
+++ b/tests/topotests/ospf_basic_functionality/ospf_flood_reduction.json
@@ -0,0 +1,214 @@
+{
+
+    "ipv4base": "10.0.0.0",
+    "ipv4mask": 24,
+    "link_ip_start": {
+        "ipv4": "10.0.0.0",
+        "v4mask": 24
+    },
+    "lo_prefix": {
+        "ipv4": "1.0.",
+        "v4mask": 32
+    },
+    "routers": {
+        "r0": {
+            "links": {
+                "lo": {
+                    "ipv4": "auto",
+                    "type": "loopback"
+                },
+                "r1": {
+                    "ipv4": "auto",
+                    "ospf": {
+                        "area": "0.0.0.0",
+                        "hello_interval": 1,
+                        "dead_interval": 4
+                    }
+                },
+                "r2": {
+                    "ipv4": "auto",
+                    "ospf": {
+                        "area": "0.0.0.0",
+                        "hello_interval": 1,
+                        "dead_interval": 4
+                    }
+                },
+                "r3": {
+                    "ipv4": "auto",
+                    "ospf": {
+                        "area": "0.0.0.0",
+                        "hello_interval": 1,
+                        "dead_interval": 4,
+                        "network": "point-to-point"
+                    }
+                }
+            },
+            "ospf": {
+                "router_id": "100.1.1.0",
+                "neighbors": {
+                    "r1": {},
+                    "r2": {},
+                    "r3": {}
+                },
+                "graceful-restart": {
+                    "helper-only": []
+                }
+            }
+        },
+        "r1": {
+            "links": {
+                "lo": {
+                    "ipv4": "auto",
+                    "type": "loopback"
+                },
+                "r0": {
+                    "ipv4": "auto",
+                    "ospf": {
+                        "area": "0.0.0.0",
+                        "hello_interval": 1,
+                        "dead_interval": 4
+                    }
+                },
+                "r2": {
+                    "ipv4": "auto",
+                    "ospf": {
+                        "area": "0.0.0.1",
+                        "hello_interval": 1,
+                        "dead_interval": 4
+                    }
+                },
+                "r3": {
+                    "ipv4": "auto",
+                    "ospf": {
+                        "area": "0.0.0.0",
+                        "hello_interval": 1,
+                        "dead_interval": 4
+                    }
+                },
+                "r3-link0": {
+                    "ipv4": "auto",
+                    "description": "DummyIntftoR3"
+                }
+            },
+            "ospf": {
+                "router_id": "100.1.1.1",
+                "neighbors": {
+                    "r0": {},
+                    "r2": {},
+                    "r3": {}
+                },
+                "graceful-restart": {
+                    "helper-only": []
+                }
+            }
+        },
+        "r2": {
+            "links": {
+                "lo": {
+                    "ipv4": "auto",
+                    "type": "loopback"
+                },
+                "r0": {
+                    "ipv4": "auto",
+                    "ospf": {
+                        "area": "0.0.0.0",
+                        "hello_interval": 1,
+                        "dead_interval": 4
+                    }
+                },
+                "r1": {
+                    "ipv4": "auto",
+                    "ospf": {
+                        "area": "0.0.0.1",
+                        "hello_interval": 1,
+                        "dead_interval": 4
+                    }
+                },
+                "r3": {
+                    "ipv4": "auto",
+                    "ospf": {
+                        "area": "0.0.0.2",
+                        "hello_interval": 1,
+                        "dead_interval": 4,
+                        "network": "broadcast"
+                    }
+                }
+            },
+            "ospf": {
+                "router_id": "100.1.1.2",
+                "area": [
+                    {
+                        "id": "0.0.0.2",
+                        "type": "nssa"
+                    }
+                ],
+                "neighbors": {
+                    "r1": {},
+                    "r0": {},
+                    "r3": {}
+                },
+                "graceful-restart": {
+                    "helper-only": []
+                }
+            }
+        },
+        "r3": {
+            "links": {
+                "lo": {
+                    "ipv4": "auto",
+                    "type": "loopback"
+                },
+                "r0": {
+                    "ipv4": "auto",
+                    "ospf": {
+                        "area": "0.0.0.0",
+                        "hello_interval": 1,
+                        "dead_interval": 4,
+                        "network": "point-to-point"
+                    }
+                },
+                "r1": {
+                    "ipv4": "auto",
+                    "ospf": {
+                        "area": "0.0.0.0",
+                        "hello_interval": 1,
+                        "dead_interval": 4
+                    }
+                },
+                "r2": {
+                    "ipv4": "auto",
+                    "ospf": {
+                        "area": "0.0.0.2",
+                        "hello_interval": 1,
+                        "dead_interval": 4,
+                        "network": "broadcast"
+                    }
+                },
+                "r1-link0": {
+                    "ipv4": "auto",
+                    "description": "DummyIntftoR1",
+                    "ospf": {
+                        "area": "0.0.0.0"
+                    }
+                }
+            },
+            "ospf": {
+                "router_id": "100.1.1.3",
+                "area": [
+                    {
+                        "id": "0.0.0.2",
+                        "type": "nssa"
+                    }
+                ],
+                "neighbors": {
+                    "r0": {},
+                    "r1": {},
+                    "r2": {}
+                },
+                "graceful-restart": {
+                    "helper-only": []
+                }
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/tests/topotests/ospf_basic_functionality/test_ospf_flood_reduction.py b/tests/topotests/ospf_basic_functionality/test_ospf_flood_reduction.py
new file mode 100644
index 000000000..bd7db644d
--- /dev/null
+++ b/tests/topotests/ospf_basic_functionality/test_ospf_flood_reduction.py
@@ -0,0 +1,1066 @@
+#!/usr/bin/python
+
+#
+# Copyright (c) 2022 by VMware, Inc. ("VMware")
+# Used Copyright (c) 2018 by Network Device Education Foundation, Inc.
+# ("NetDEF") in this file.
+#
+# Permission to use, copy, modify, and/or distribute this software
+# for any purpose with or without fee is hereby granted, provided
+# that the above copyright notice and this permission notice appear
+# in all copies.
+#
+# THE SOFTWARE IS PROVIDED "AS IS" AND VMWARE DISCLAIMS ALL WARRANTIES
+# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL VMWARE BE LIABLE FOR
+# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY
+# DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
+# WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
+# ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+# OF THIS SOFTWARE.
+#
+
+
+"""OSPF Basic Functionality Automation."""
+import os
+import sys
+import time
+import pytest
+from time import sleep
+
+# Save the Current Working Directory to find configuration files.
+CWD = os.path.dirname(os.path.realpath(__file__))
+sys.path.append(os.path.join(CWD, "../"))
+sys.path.append(os.path.join(CWD, "../lib/"))
+
+pytestmark = [pytest.mark.ospfd, pytest.mark.staticd]
+# Global variables
+topo = None
+
+# pylint: disable=C0413
+# Import topogen and topotest helpers
+from lib.topolog import logger
+from lib.topojson import build_config_from_json
+
+# Import topoJson from lib, to create topology and initial configuration
+from lib.common_config import (
+    start_topology,
+    write_test_header,
+    write_test_footer,
+    reset_config_on_routers,
+    create_static_routes,
+    step,
+    topo_daemons,
+    shutdown_bringup_interface,
+    check_router_status,
+    start_topology,
+    write_test_header,
+    write_test_footer,
+    reset_config_on_routers,
+    create_static_routes,
+    step,
+    shutdown_bringup_interface,
+    check_router_status,
+    start_topology,
+    write_test_header,
+    write_test_footer,
+    reset_config_on_routers,
+    stop_router,
+    start_router,
+    step,
+    create_static_routes,
+    kill_router_daemons,
+    check_router_status,
+    start_router_daemons,
+)
+from lib.topolog import logger
+from lib.topogen import Topogen, get_topogen
+
+from lib.topojson import build_config_from_json
+from lib.ospf import (
+    verify_ospf_neighbor,
+    clear_ospf,
+    create_router_ospf,
+    verify_ospf_database,
+    get_ospf_database,
+)
+
+# Global variables
+topo = None
+NETWORK = {
+    "ipv4": [
+        "11.0.20.1/32",
+        "11.0.20.2/32",
+        "11.0.20.3/32",
+        "11.0.20.4/32",
+        "11.0.20.5/32",
+    ]
+}
+"""
+TOPOOLOGY =
+      Please view in a fixed-width font such as Courier.
+      +---+  A1       +---+
+      +R1 +------------+R2 |
+      +-+-+-           +--++
+        |  --        --  |
+        |    -- A0 --    |
+      A0|      ----      |
+        |      ----      | A2
+        |    --    --    |
+        |  --        --  |
+      +-+-+-            +-+-+
+      +R0 +-------------+R3 |
+      +---+     A3     +---+
+
+TESTCASES =
+1. Verify OSPF Flood reduction functionality with ospf enabled on process level.
+2. Verify OSPF Flood reduction functionality with ospf enabled on area level.
+3. Verify OSPF Flood reduction functionality between different area's.
+4. Verify OSPF Flood reduction functionality with ospf enabled on process level with default lsa refresh timer.
+5. Chaos - Verify OSPF TTL GTSM and flood  reduction functionality in chaos scenarios.
+"""
+
+
+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)
+
+    logger.info("Running setup_module to create topology")
+
+    # This function initiates the topology build with Topogen...
+    json_file = "{}/ospf_flood_reduction.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.
+    daemons = topo_daemons(tgen)
+
+    # Starting topology, create tmp files which are loaded to routers
+    #  to start daemons and then start routers
+    start_topology(tgen)
+
+    # Creating configuration from JSON
+    build_config_from_json(tgen, topo)
+
+    # Don't run this test if we have any failure.
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
+    # Api call verify whether OSPF is converged
+    ospf_covergence = verify_ospf_neighbor(tgen, topo)
+    assert ospf_covergence is True, "setup_module :Failed \n Error:" " {}".format(
+        ospf_covergence
+    )
+
+    logger.info("Running setup_module() done")
+
+
+def teardown_module(mod):
+    """
+    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()
+
+    logger.info(
+        "Testsuite end time: {}".format(time.asctime(time.localtime(time.time())))
+    )
+    logger.info("=" * 40)
+
+
+
+def red_static(dut, config=True):
+    """Local def for Redstribute static routes inside ospf."""
+    global topo
+    tgen = get_topogen()
+    if config:
+        ospf_red = {dut: {"ospf": {"redistribute": [{"redist_type": "static"}]}}}
+    else:
+        ospf_red = {
+            dut: {
+                "ospf": {
+                    "redistribute": [{"redist_type": "static", "del_action": True}]
+                }
+            }
+        }
+    result = create_router_ospf(tgen, topo, ospf_red)
+    assert result is True, "Testcase : Failed \n Error: {}".format(result)
+
+
+# ##################################
+# Test cases start here.
+# ##################################
+def test_ospf_flood_red_tc1_p0(request):
+    """Verify OSPF Flood reduction functionality with ospf enabled on process level."""
+    tc_name = request.node.name
+    write_test_header(tc_name)
+    tgen = get_topogen()
+
+    # Don't run this test if we have any failure.
+    if tgen.routers_have_failure():
+        check_router_status(tgen)
+
+    global topo
+
+    step("Bring up the base config as per the topology")
+    reset_config_on_routers(tgen)
+    red_static("r0")
+    step("Base config should be up, verify using OSPF convergence on all the routers")
+
+    ospf_covergence = verify_ospf_neighbor(tgen, topo)
+    assert ospf_covergence is True, "Testcase :Failed \n Error:" " {}".format(
+        ospf_covergence
+    )
+
+    input_dict = {
+        "r0": {
+            "static_routes": [
+                {
+                    "network": NETWORK["ipv4"][0],
+                    "no_of_ip": 5,
+                    "next_hop": "Null0",
+                }
+            ]
+        }
+    }
+    result = create_static_routes(tgen, input_dict)
+    assert result is True, "Testcase {} : Failed \n Error: {}".format(tc_name, result)
+
+    step("Enable flood reduction in process level on R0")
+    ospf_flood = {"r0": {"ospf": {"flood-reduction": True}}}
+    result = create_router_ospf(tgen, topo, ospf_flood)
+    assert result is True, "Testcase : Failed \n Error: {}".format(result)
+
+    step("Verify that ospf lsa's are set with dc bit 1.")
+    dut = "r0"
+    input_dict_db = {
+        "routerId": "100.1.1.0",
+        "areas": {
+            "0.0.0.0": {
+                "routerLinkStates": [
+                    {
+                        "lsaId": "100.1.1.0",
+                        "options": "*|-|DC|-|-|-|E|-",
+                    },
+                ]
+            }
+        },
+    }
+    result = verify_ospf_database(
+        tgen, topo, dut, input_dict_db, lsatype="router", rid="100.1.1.0"
+    )
+    assert result is True, "Testcase {} : Failed \n Error: {}".format(tc_name, result)
+
+    step("Configure the custom refresh timer")
+    ospf_flood = {"r0": {"ospf": {"lsa-refresh": 120}}}
+    result = create_router_ospf(tgen, topo, ospf_flood)
+    assert result is True, "Testcase : Failed \n Error: {}".format(result)
+
+    step("Enable flood. reduction in all the routers of the topology.")
+    for rtr in topo["routers"].keys():
+        ospf_flood = {rtr: {"ospf": {"lsa-refresh": 120, "flood-reduction": True}}}
+        result = create_router_ospf(tgen, topo, ospf_flood)
+        assert result is True, "Testcase : Failed \n Error: {}".format(result)
+
+    for rtr in topo["routers"]:
+        clear_ospf(tgen, rtr)
+
+    ospf_covergence = verify_ospf_neighbor(tgen, topo)
+    assert ospf_covergence is True, "Testcase :Failed \n Error:" " {}".format(
+        ospf_covergence
+    )
+
+    step("Verify that ospf lsa's are set with dc bit 1.")
+    for rtr in topo["routers"]:
+        dut = rtr
+        lsid = "{}".format(topo["routers"][rtr]["ospf"]["router_id"])
+        input_dict_db = {
+            "routerId": lsid,
+            "areas": {
+                "0.0.0.0": {
+                    "routerLinkStates": [
+                        {
+                            "lsaId": lsid,
+                            "options": "*|-|DC|-|-|-|E|-",
+                        },
+                    ]
+                }
+            },
+        }
+        result = verify_ospf_database(
+            tgen, topo, dut, input_dict_db, lsatype="router", rid=lsid
+        )
+        assert result is True, "Testcase {} : Failed \n Error: {}".format(
+            tc_name, result
+        )
+
+    step("Wait for 120 secs and verify that LSA's are not refreshed. ")
+    # get LSA age
+    dut = "r1"
+    input_dict_db = {
+        "routerId": "100.1.1.0",
+        "areas": {
+            "0.0.0.0": {
+                "routerLinkStates": [
+                    {"lsaId": "100.1.1.0", "lsaAge": "get"},
+                ]
+            }
+        },
+    }
+    sleep(10)
+
+    result1 = get_ospf_database(
+        tgen, topo, dut, input_dict_db, lsatype="router", rid="100.1.1.0"
+    )
+    # this wait is put so that we wait for 5secs to check if lsa is refreshed.
+    sleep(5)
+    result2 = get_ospf_database(
+        tgen, topo, dut, input_dict_db, lsatype="router", rid="100.1.1.0"
+    )
+
+    assert (result1 == result2) is True, "Testcase {} : Failed \n Error: {}".format(
+        tc_name, result
+    )
+
+    step("Disable flood reduction in R0.")
+    ospf_flood = {
+        "r0": {"ospf": {"flood-reduction": True, "del_flood_reduction": True}}
+    }
+    result = create_router_ospf(tgen, topo, ospf_flood)
+    assert result is True, "Testcase : Failed \n Error: {}".format(result)
+
+    clear_ospf(tgen, "r0")
+
+    ospf_covergence = verify_ospf_neighbor(tgen, topo)
+    assert ospf_covergence is True, "Testcase :Failed \n Error:" " {}".format(
+        ospf_covergence
+    )
+
+    step("Verify that ospf lea's are not set with dc bit 1.")
+    dut = "r0"
+    input_dict_db = {
+        "routerId": "100.1.1.0",
+        "areas": {
+            "0.0.0.0": {
+                "routerLinkStates": [
+                    {
+                        "lsaId": "100.1.1.0",
+                        "options": "*|-|DC|-|-|-|E|-",
+                    },
+                ]
+            }
+        },
+    }
+    result = verify_ospf_database(
+        tgen, topo, dut, input_dict_db, lsatype="router", rid="100.1.1.0", expected=False
+    )
+    assert result is not True, (
+        "Testcase {} : Failed \n "
+        "Expected: OSPF LSA should not be set with DC bit in {} \n "
+        "Found: {}".format(tc_name, dut, result)
+    )
+    step("Wait for 120 secs and verify that LSA's are not refreshed. ")
+    # get LSA age
+    dut = "r1"
+    input_dict_db = {
+        "routerId": "100.1.1.0",
+        "areas": {
+            "0.0.0.0": {
+                "routerLinkStates": [
+                    {"lsaId": "100.1.1.0", "lsaAge": "get"},
+                ]
+            }
+        },
+    }
+    sleep(10)
+
+    result1 = get_ospf_database(
+        tgen, topo, dut, input_dict_db, lsatype="router", rid="100.1.1.0"
+    )
+    sleep(5)
+    result2 = get_ospf_database(
+        tgen, topo, dut, input_dict_db, lsatype="router", rid="100.1.1.0"
+    )
+
+    if result2 is not result1:
+        result = True
+    assert result is True, "Testcase {} : Failed \n Error: {}".format(tc_name, result)
+
+    step(
+        "Enable flood reduction on each router with 10 secs delay of between each router."
+    )
+    for rtr in topo["routers"].keys():
+        ospf_flood = {rtr: {"ospf": {"lsa-refresh": 120, "flood-reduction": True}}}
+        sleep(10)
+        result = create_router_ospf(tgen, topo, ospf_flood)
+        assert result is True, "Testcase : Failed \n Error: {}".format(result)
+
+    for rtr in topo["routers"]:
+        clear_ospf(tgen, rtr)
+
+    step("Verify that LSA's are not refreshed. Do not age bit should be set to 1.")
+    dut = "r0"
+    input_dict_db = {
+        "routerId": "100.1.1.0",
+        "areas": {
+            "0.0.0.0": {
+                "routerLinkStates": [
+                    {
+                        "lsaId": "100.1.1.0",
+                        "options": "*|-|DC|-|-|-|E|-",
+                    },
+                ]
+            }
+        },
+    }
+    result = verify_ospf_database(
+        tgen, topo, dut, input_dict_db, lsatype="router", rid="100.1.1.0"
+    )
+    assert result is True, "Testcase {} : Failed \n Error: {}".format(tc_name, result)
+
+    step(
+        "Verify OSPF neighborship when OSPF flood reduction  is configured and ospf process is restarted"
+    )
+
+    step("Kill OSPFd daemon on R0.")
+    kill_router_daemons(tgen, "r0", ["ospfd"])
+    start_router_daemons(tgen, "r0", ["ospfd"])
+
+    ospf_covergence = verify_ospf_neighbor(tgen, topo)
+    assert ospf_covergence is True, "Testcase :Failed \n Error:" " {}".format(
+        ospf_covergence
+    )
+
+    step("Verify that LSA's are not refreshed. Do not age bit should be set to 1.")
+    dut = "r0"
+    input_dict_db = {
+        "routerId": "100.1.1.0",
+        "areas": {
+            "0.0.0.0": {
+                "routerLinkStates": [
+                    {
+                        "lsaId": "100.1.1.0",
+                        "options": "*|-|DC|-|-|-|E|-",
+                    },
+                ]
+            }
+        },
+    }
+    result = verify_ospf_database(
+        tgen, topo, dut, input_dict_db, lsatype="router", rid="100.1.1.0"
+    )
+    assert result is True, "Testcase {} : Failed \n Error: {}".format(tc_name, result)
+
+    write_test_footer(tc_name)
+
+
+def test_ospf_flood_red_tc2_p0(request):
+    """Verify OSPF Flood reduction functionality with ospf enabled on area level."""
+    tc_name = request.node.name
+    write_test_header(tc_name)
+    tgen = get_topogen()
+
+    # Don't run this test if we have any failure.
+    if tgen.routers_have_failure():
+        check_router_status(tgen)
+
+    global topo
+
+    step("Bring up the base config as per the topology")
+    reset_config_on_routers(tgen)
+    red_static("r0")
+    step("Base config should be up, verify using OSPF convergence on all the routers")
+
+    ospf_covergence = verify_ospf_neighbor(tgen, topo)
+    assert ospf_covergence is True, "Testcase :Failed \n Error:" " {}".format(
+        ospf_covergence
+    )
+
+    input_dict = {
+        "r0": {
+            "static_routes": [
+                {
+                    "network": NETWORK["ipv4"][0],
+                    "no_of_ip": 5,
+                    "next_hop": "Null0",
+                }
+            ]
+        }
+    }
+    result = create_static_routes(tgen, input_dict)
+    assert result is True, "Testcase {} : Failed \n Error: {}".format(tc_name, result)
+
+    step("Enable flood reduction in area level on R0 in area 0")
+    ospf_flood = {
+        "r0": {"ospf": {"area": [{"id": "0.0.0.0", "flood-reduction": True}]}}
+    }
+    result = create_router_ospf(tgen, topo, ospf_flood)
+    assert result is True, "Testcase : Failed \n Error: {}".format(result)
+
+    step("Verify that ospf lsa's are set with dc bit 1.")
+    dut = "r0"
+    input_dict_db = {
+        "routerId": "100.1.1.0",
+        "areas": {
+            "0.0.0.0": {
+                "routerLinkStates": [
+                    {
+                        "lsaId": "100.1.1.0",
+                        "options": "*|-|DC|-|-|-|E|-",
+                    },
+                ]
+            }
+        },
+    }
+    result = verify_ospf_database(
+        tgen, topo, dut, input_dict_db, lsatype="router", rid="100.1.1.0"
+    )
+    assert result is True, "Testcase {} : Failed \n Error: {}".format(tc_name, result)
+
+    step("Configure the custom refresh timer")
+    ospf_flood = {"r0": {"ospf": {"lsa-refresh": 120}}}
+    result = create_router_ospf(tgen, topo, ospf_flood)
+    assert result is True, "Testcase : Failed \n Error: {}".format(result)
+
+    step("Enable flood. reduction in all the routers of the topology.")
+    for rtr in topo["routers"].keys():
+        ospf_flood = {
+            rtr: {"ospf": {"area": [{"id": "0.0.0.0", "flood-reduction": True}]}}
+        }
+        result = create_router_ospf(tgen, topo, ospf_flood)
+        assert result is True, "Testcase : Failed \n Error: {}".format(result)
+
+    for rtr in topo["routers"]:
+        clear_ospf(tgen, rtr)
+
+    ospf_covergence = verify_ospf_neighbor(tgen, topo)
+    assert ospf_covergence is True, "Testcase :Failed \n Error:" " {}".format(
+        ospf_covergence
+    )
+
+    step("Verify that ospf lsa's are set with dc bit 1.")
+    for rtr in topo["routers"]:
+        dut = rtr
+        lsid = "{}".format(topo["routers"][rtr]["ospf"]["router_id"])
+        input_dict_db = {
+            "routerId": lsid,
+            "areas": {
+                "0.0.0.0": {
+                    "routerLinkStates": [
+                        {
+                            "lsaId": lsid,
+                            "options": "*|-|DC|-|-|-|E|-",
+                        },
+                    ]
+                }
+            },
+        }
+        result = verify_ospf_database(
+            tgen, topo, dut, input_dict_db, lsatype="router", rid=lsid
+        )
+        assert result is True, "Testcase {} : Failed \n Error: {}".format(tc_name, result)
+
+    step("Wait for 120 secs and verify that LSA's are not refreshed. ")
+    # get LSA age
+    dut = "r1"
+    input_dict_db = {
+        "routerId": "100.1.1.0",
+        "areas": {
+            "0.0.0.0": {
+                "routerLinkStates": [
+                    {"lsaId": "100.1.1.0", "lsaAge": "get"},
+                ]
+            }
+        },
+    }
+    sleep(10)
+
+    result1 = get_ospf_database(
+        tgen, topo, dut, input_dict_db, lsatype="router", rid="100.1.1.0"
+    )
+    sleep(5)
+    result2 = get_ospf_database(
+        tgen, topo, dut, input_dict_db, lsatype="router", rid="100.1.1.0"
+    )
+
+    assert (result1 == result2) is True, "Testcase {} : Failed \n Error: {}".format(
+        tc_name, result
+    )
+
+    step("Disable flood reduction in R0.")
+    ospf_flood = {
+        "r0": {
+            "ospf": {
+                "area": [{"id": "0.0.0.0", "flood-reduction": True, "delete": True}]
+            }
+        }
+    }
+    result = create_router_ospf(tgen, topo, ospf_flood)
+    assert result is True, "Testcase : Failed \n Error: {}".format(result)
+
+    clear_ospf(tgen, "r0")
+
+    ospf_covergence = verify_ospf_neighbor(tgen, topo)
+    assert ospf_covergence is True, "Testcase :Failed \n Error:" " {}".format(
+        ospf_covergence
+    )
+
+    step("Verify that ospf lea's are not set with dc bit 1.")
+    dut = "r0"
+    input_dict_db = {
+        "routerId": "100.1.1.0",
+        "areas": {
+            "0.0.0.0": {
+                "routerLinkStates": [
+                    {
+                        "lsaId": "100.1.1.0",
+                        "options": "*|-|DC|-|-|-|E|-",
+                    },
+                ]
+            }
+        },
+    }
+    result = verify_ospf_database(
+        tgen, topo, dut, input_dict_db, lsatype="router", rid="100.1.1.0", expected=False
+    )
+    assert result is not True, (
+        "Testcase {} : Failed \n "
+        "Expected: OSPF LSA should not be set with DC bit in {} \n "
+        "Found: {}".format(tc_name, dut, result)
+    )
+    step("Wait for 120 secs and verify that LSA's are not refreshed. ")
+    # get LSA age
+    dut = "r1"
+    input_dict_db = {
+        "routerId": "100.1.1.0",
+        "areas": {
+            "0.0.0.0": {
+                "routerLinkStates": [
+                    {"lsaId": "100.1.1.0", "lsaAge": "get"},
+                ]
+            }
+        },
+    }
+    sleep(10)
+
+    result1 = get_ospf_database(
+        tgen, topo, dut, input_dict_db, lsatype="router", rid="100.1.1.0"
+    )
+    sleep(5)
+    result2 = get_ospf_database(
+        tgen, topo, dut, input_dict_db, lsatype="router", rid="100.1.1.0"
+    )
+
+    if result2 is not result1:
+        result = True
+    assert result is True, "Testcase {} : Failed \n Error: {}".format(tc_name, result)
+
+    step(
+        "Enable flood reduction on each router with 10 secs delay of between each router."
+    )
+    for rtr in topo["routers"].keys():
+        ospf_flood = {
+            rtr: {"ospf": {"area": [{"id": "0.0.0.0", "flood-reduction": True}]}}
+        }
+        sleep(10)
+        result = create_router_ospf(tgen, topo, ospf_flood)
+        assert result is True, "Testcase : Failed \n Error: {}".format(result)
+
+    for rtr in topo["routers"]:
+        clear_ospf(tgen, rtr)
+
+    step("Verify that LSA's are not refreshed. Do not age bit should be set to 1.")
+    dut = "r0"
+    input_dict_db = {
+        "routerId": "100.1.1.0",
+        "areas": {
+            "0.0.0.0": {
+                "routerLinkStates": [
+                    {
+                        "lsaId": "100.1.1.0",
+                        "options": "*|-|DC|-|-|-|E|-",
+                    },
+                ]
+            }
+        },
+    }
+    result = verify_ospf_database(
+        tgen, topo, dut, input_dict_db, lsatype="router", rid="100.1.1.0"
+    )
+    assert result is True, "Testcase {} : Failed \n Error: {}".format(tc_name, result)
+
+    write_test_footer(tc_name)
+
+
+def test_ospf_flood_red_tc3_p0(request):
+    """Verify OSPF Flood reduction functionality between different area's"""
+    tc_name = request.node.name
+    write_test_header(tc_name)
+    tgen = get_topogen()
+
+    # Don't run this test if we have any failure.
+    if tgen.routers_have_failure():
+        check_router_status(tgen)
+
+    global topo
+
+    step("Bring up the base config as per the topology")
+    reset_config_on_routers(tgen)
+    red_static("r0")
+    step("Base config should be up, verify using OSPF convergence on all the routers")
+
+    ospf_covergence = verify_ospf_neighbor(tgen, topo)
+    assert ospf_covergence is True, "Testcase :Failed \n Error:" " {}".format(
+        ospf_covergence
+    )
+
+    input_dict = {
+        "r0": {
+            "static_routes": [
+                {
+                    "network": NETWORK["ipv4"][0],
+                    "no_of_ip": 5,
+                    "next_hop": "Null0",
+                }
+            ]
+        }
+    }
+    result = create_static_routes(tgen, input_dict)
+    assert result is True, "Testcase {} : Failed \n Error: {}".format(tc_name, result)
+
+    step("Enable flood reduction in area level on R0 in area 0")
+    ospf_flood = {
+        "r0": {"ospf": {"area": [{"id": "0.0.0.0", "flood-reduction": True}]}}
+    }
+    result = create_router_ospf(tgen, topo, ospf_flood)
+    assert result is True, "Testcase : Failed \n Error: {}".format(result)
+
+    step("Verify that ospf lsa's are set with dc bit 1.")
+    dut = "r0"
+    input_dict_db = {
+        "routerId": "100.1.1.0",
+        "areas": {
+            "0.0.0.0": {
+                "routerLinkStates": [
+                    {
+                        "lsaId": "100.1.1.0",
+                        "options": "*|-|DC|-|-|-|E|-",
+                    },
+                ]
+            }
+        },
+    }
+    result = verify_ospf_database(
+        tgen, topo, dut, input_dict_db, lsatype="router", rid="100.1.1.0"
+    )
+    assert result is True, "Testcase {} : Failed \n Error: {}".format(tc_name, result)
+
+    step("Configure the custom refresh timer")
+    ospf_flood = {"r0": {"ospf": {"lsa-refresh": 120}}}
+    result = create_router_ospf(tgen, topo, ospf_flood)
+    assert result is True, "Testcase : Failed \n Error: {}".format(result)
+
+    step(
+        "Enable flood. reduction in all the routers of the topology in area 0. Redistribute static route in area 0 R1 and area1 in R2."
+    )
+    for rtr in topo["routers"].keys():
+        ospf_flood = {
+            rtr: {"ospf": {"area": [{"id": "0.0.0.0", "flood-reduction": True}]}}
+        }
+        result = create_router_ospf(tgen, topo, ospf_flood)
+        assert result is True, "Testcase : Failed \n Error: {}".format(result)
+
+    sleep(10)
+
+    for rtr in topo["routers"]:
+        clear_ospf(tgen, rtr)
+
+    ospf_covergence = verify_ospf_neighbor(tgen, topo)
+    assert ospf_covergence is True, "Testcase :Failed \n Error:" " {}".format(
+        ospf_covergence
+    )
+
+    step("Verify that ospf lsa's are set with dc bit 1.")
+    for rtr in topo["routers"]:
+        dut = rtr
+        lsid = "{}".format(topo["routers"][rtr]["ospf"]["router_id"])
+        input_dict_db = {
+            "routerId": lsid,
+            "areas": {
+                "0.0.0.0": {
+                    "routerLinkStates": [
+                        {
+                            "lsaId": lsid,
+                            "options": "*|-|DC|-|-|-|E|-",
+                        },
+                    ]
+                }
+            },
+        }
+        result = verify_ospf_database(
+            tgen, topo, dut, input_dict_db, lsatype="router", rid=lsid
+        )
+        assert result is True, "Testcase {} : Failed \n Error: {}".format(tc_name, result)
+
+    step("Wait for 120 secs and verify that LSA's are not refreshed. ")
+    # get LSA age
+    dut = "r1"
+    input_dict_db = {
+        "routerId": "100.1.1.0",
+        "areas": {
+            "0.0.0.0": {
+                "routerLinkStates": [
+                    {"lsaId": "100.1.1.0", "lsaAge": "get"},
+                ]
+            }
+        },
+    }
+    sleep(10)
+
+    result1 = get_ospf_database(
+        tgen, topo, dut, input_dict_db, lsatype="router", rid="100.1.1.0"
+    )
+    sleep(5)
+    result2 = get_ospf_database(
+        tgen, topo, dut, input_dict_db, lsatype="router", rid="100.1.1.0"
+    )
+
+    assert (result1 == result2) is True, "Testcase {} : Failed \n Error: {}".format(
+        tc_name, result
+    )
+
+    step("Enable flood reduction in area 1.")
+
+    ospf_flood = {
+        "r0": {"ospf": {"area": [{"id": "0.0.0.0", "flood-reduction": True}]}}
+    }
+    result = create_router_ospf(tgen, topo, ospf_flood)
+    assert result is True, "Testcase : Failed \n Error: {}".format(result)
+
+    ospf_flood = {
+        "r1": {
+            "ospf": {
+                "area": [
+                    {"id": "0.0.0.0", "flood-reduction": True},
+                    {"id": "0.0.0.1", "flood-reduction": True},
+                ]
+            }
+        }
+    }
+    result = create_router_ospf(tgen, topo, ospf_flood)
+    assert result is True, "Testcase : Failed \n Error: {}".format(result)
+
+    ospf_flood = {
+        "r2": {
+            "ospf": {
+                "area": [
+                    {"id": "0.0.0.0", "flood-reduction": True},
+                    {"id": "0.0.0.1", "flood-reduction": True},
+                    {"id": "0.0.0.2", "flood-reduction": True},
+                ]
+            }
+        }
+    }
+    result = create_router_ospf(tgen, topo, ospf_flood)
+    assert result is True, "Testcase : Failed \n Error: {}".format(result)
+
+    ospf_flood = {
+        "r3": {
+            "ospf": {
+                "area": [
+                    {"id": "0.0.0.0", "flood-reduction": True},
+                    {"id": "0.0.0.2", "flood-reduction": True},
+                ]
+            }
+        }
+    }
+    result = create_router_ospf(tgen, topo, ospf_flood)
+    assert result is True, "Testcase : Failed \n Error: {}".format(result)
+
+    for rtr in topo["routers"]:
+        clear_ospf(tgen, rtr)
+
+    ospf_covergence = verify_ospf_neighbor(tgen, topo)
+    assert ospf_covergence is True, "Testcase :Failed \n Error:" " {}".format(
+        ospf_covergence
+    )
+
+    step("Verify that ospf lea's are  set with dc bit 1.")
+    dut = "r1"
+    input_dict_db = {
+        "routerId": "100.1.1.1",
+        "areas": {
+            "0.0.0.0": {
+                "routerLinkStates": [
+                    {
+                        "lsaId": "100.1.1.1",
+                        "options": "*|-|DC|-|-|-|E|-",
+                    },
+                ]
+            }
+        },
+    }
+    result = verify_ospf_database(
+        tgen, topo, dut, input_dict_db, lsatype="router", rid="100.1.1.1"
+    )
+    assert result is True, "Testcase {} : Failed \n Error: {}".format(tc_name, result)
+
+    step("Wait for 120 secs and verify that LSA's are not refreshed. ")
+    # get LSA age
+    dut = "r1"
+    input_dict_db = {
+        "routerId": "100.1.1.1",
+        "areas": {
+            "0.0.0.0": {
+                "routerLinkStates": [
+                    {"lsaId": "100.1.1.1", "lsaAge": "get"},
+                ]
+            }
+        },
+    }
+    sleep(10)
+
+    result1 = get_ospf_database(
+        tgen, topo, dut, input_dict_db, lsatype="router", rid="100.1.1.1"
+    )
+    sleep(5)
+    result2 = get_ospf_database(
+        tgen, topo, dut, input_dict_db, lsatype="router", rid="100.1.1.1"
+    )
+
+    if result2 is result1:
+        result = True
+    assert result is True, "Testcase {} : Failed \n Error: {}".format(tc_name, result)
+
+    step("Disable flood reduction in R0.")
+
+    ospf_flood = {
+        "r0": {
+            "ospf": {
+                "area": [{"id": "0.0.0.0", "flood-reduction": True, "delete": True}]
+            }
+        }
+    }
+    result = create_router_ospf(tgen, topo, ospf_flood)
+    assert result is True, "Testcase : Failed \n Error: {}".format(result)
+
+    ospf_flood = {
+        "r1": {
+            "ospf": {
+                "area": [
+                    {"id": "0.0.0.0", "flood-reduction": True, "delete": True},
+                    {"id": "0.0.0.1", "flood-reduction": True, "delete": True},
+                ]
+            }
+        }
+    }
+    result = create_router_ospf(tgen, topo, ospf_flood)
+    assert result is True, "Testcase : Failed \n Error: {}".format(result)
+
+    ospf_flood = {
+        "r2": {
+            "ospf": {
+                "area": [
+                    {"id": "0.0.0.0", "flood-reduction": True, "delete": True},
+                    {"id": "0.0.0.1", "flood-reduction": True, "delete": True},
+                    {"id": "0.0.0.2", "flood-reduction": True, "delete": True},
+                ]
+            }
+        }
+    }
+    result = create_router_ospf(tgen, topo, ospf_flood)
+    assert result is True, "Testcase : Failed \n Error: {}".format(result)
+
+    ospf_flood = {
+        "r3": {
+            "ospf": {
+                "area": [
+                    {"id": "0.0.0.0", "flood-reduction": True, "delete": True},
+                    {"id": "0.0.0.2", "flood-reduction": True, "delete": True},
+                ]
+            }
+        }
+    }
+    result = create_router_ospf(tgen, topo, ospf_flood)
+    assert result is True, "Testcase : Failed \n Error: {}".format(result)
+
+    clear_ospf(tgen, "r0")
+
+    ospf_covergence = verify_ospf_neighbor(tgen, topo)
+    assert ospf_covergence is True, "Testcase :Failed \n Error:" " {}".format(
+        ospf_covergence
+    )
+
+    step("Verify that ospf lea's are not set with dc bit 1.")
+    dut = "r0"
+    input_dict_db = {
+        "routerId": "100.1.1.0",
+        "areas": {
+            "0.0.0.0": {
+                "routerLinkStates": [
+                    {
+                        "lsaId": "100.1.1.0",
+                        "options": "*|-|DC|-|-|-|E|-",
+                    },
+                ]
+            }
+        },
+    }
+    result = verify_ospf_database(
+        tgen, topo, dut, input_dict_db, lsatype="router", rid="100.1.1.0", expected=False
+    )
+
+    assert result is not True, (
+        "Testcase {} : Failed \n "
+        "Expected: OSPF LSA should not be set with DC bit in {} \n "
+        "Found: {}".format(tc_name, dut, result)
+    )
+
+    step("Wait for 120 secs and verify that LSA's are not refreshed. ")
+    # get LSA age
+    dut = "r1"
+    input_dict_db = {
+        "routerId": "100.1.1.0",
+        "areas": {
+            "0.0.0.0": {
+                "routerLinkStates": [
+                    {"lsaId": "100.1.1.0", "lsaAge": "get"},
+                ]
+            }
+        },
+    }
+    sleep(10)
+
+    result1 = get_ospf_database(
+        tgen, topo, dut, input_dict_db, lsatype="router", rid="100.1.1.0"
+    )
+    sleep(5)
+    result2 = get_ospf_database(
+        tgen, topo, dut, input_dict_db, lsatype="router", rid="100.1.1.0"
+    )
+
+    if result2 is not result1:
+        result = True
+    assert result is True, "Testcase {} : Failed \n Error: {}".format(tc_name, result)
+
+    write_test_footer(tc_name)
+
+
+if __name__ == "__main__":
+    args = ["-s"] + sys.argv[1:]
+    sys.exit(pytest.main(args))