diff --git a/isisd/isis_adjacency.c b/isisd/isis_adjacency.c
index 72e6d4bdb9..ece080347d 100644
--- a/isisd/isis_adjacency.c
+++ b/isisd/isis_adjacency.c
@@ -47,6 +47,7 @@
 #include "isisd/isis_spf.h"
 #include "isisd/isis_events.h"
 #include "isisd/isis_mt.h"
+#include "isisd/isis_tlvs.h"
 
 extern struct isis *isis;
 
@@ -78,6 +79,7 @@ struct isis_adjacency *isis_new_adj(const u_char *id, const u_char *snpa,
 	adj->level = level;
 	adj->flaps = 0;
 	adj->last_flap = time(NULL);
+	adj->threeway_state = ISIS_THREEWAY_DOWN;
 	if (circuit->circ_type == CIRCUIT_T_BROADCAST) {
 		listnode_add(circuit->u.bc.adjdb[level - 1], adj);
 		adj->dischanges[level - 1] = 0;
@@ -161,6 +163,51 @@ static const char *adj_state2string(int state)
 	return NULL; /* not reached */
 }
 
+void isis_adj_process_threeway(struct isis_adjacency *adj,
+			       struct isis_threeway_adj *tw_adj,
+			       enum isis_adj_usage adj_usage)
+{
+	enum isis_threeway_state next_tw_state = ISIS_THREEWAY_DOWN;
+
+	if (tw_adj) {
+		if (tw_adj->state == ISIS_THREEWAY_DOWN) {
+			next_tw_state = ISIS_THREEWAY_INITIALIZING;
+		} else if (tw_adj->state == ISIS_THREEWAY_INITIALIZING) {
+			next_tw_state = ISIS_THREEWAY_UP;
+		} else if (tw_adj->state == ISIS_THREEWAY_UP) {
+			if (adj->threeway_state == ISIS_THREEWAY_DOWN)
+				next_tw_state = ISIS_THREEWAY_DOWN;
+			else
+				next_tw_state = ISIS_THREEWAY_UP;
+		}
+	} else {
+		next_tw_state = ISIS_THREEWAY_UP;
+	}
+
+	if (next_tw_state != adj->threeway_state) {
+		if (isis->debugs & DEBUG_ADJ_PACKETS) {
+			zlog_info("ISIS-Adj (%s): Threeway state change %s to %s",
+				  adj->circuit->area->area_tag,
+				  isis_threeway_state_name(adj->threeway_state),
+				  isis_threeway_state_name(next_tw_state));
+		}
+	}
+
+	if (next_tw_state == ISIS_THREEWAY_DOWN) {
+		isis_adj_state_change(adj, ISIS_ADJ_DOWN, "Neighbor restarted");
+		return;
+	}
+
+	if (next_tw_state == ISIS_THREEWAY_UP) {
+		if (adj->adj_state != ISIS_ADJ_UP) {
+			isis_adj_state_change(adj, ISIS_ADJ_UP, NULL);
+			adj->adj_usage = adj_usage;
+		}
+	}
+
+	adj->threeway_state = next_tw_state;
+}
+
 void isis_adj_state_change(struct isis_adjacency *adj,
 			   enum isis_adj_state new_state, const char *reason)
 {
diff --git a/isisd/isis_adjacency.h b/isisd/isis_adjacency.h
index 98bb9838fa..2c3bd19af8 100644
--- a/isisd/isis_adjacency.h
+++ b/isisd/isis_adjacency.h
@@ -25,6 +25,8 @@
 #ifndef _ZEBRA_ISIS_ADJACENCY_H
 #define _ZEBRA_ISIS_ADJACENCY_H
 
+#include "isisd/isis_tlvs.h"
+
 enum isis_adj_usage {
 	ISIS_ADJ_NONE,
 	ISIS_ADJ_LEVEL1,
@@ -91,6 +93,8 @@ struct isis_adjacency {
 	u_int16_t hold_time;		/* entryRemainingTime */
 	u_int32_t last_upd;
 	u_int32_t last_flap;	  /* last time the adj flapped */
+	enum isis_threeway_state threeway_state;
+	uint32_t ext_circuit_id;
 	int flaps;		      /* number of adjacency flaps  */
 	struct thread *t_expire;      /* expire after hold_time  */
 	struct isis_circuit *circuit; /* back pointer */
@@ -98,12 +102,17 @@ struct isis_adjacency {
 	unsigned int mt_count; /* Number of entries in mt_set */
 };
 
+struct isis_threeway_adj;
+
 struct isis_adjacency *isis_adj_lookup(const u_char *sysid, struct list *adjdb);
 struct isis_adjacency *isis_adj_lookup_snpa(const u_char *ssnpa,
 					    struct list *adjdb);
 struct isis_adjacency *isis_new_adj(const u_char *id, const u_char *snpa,
 				    int level, struct isis_circuit *circuit);
 void isis_delete_adj(void *adj);
+void isis_adj_process_threeway(struct isis_adjacency *adj,
+			       struct isis_threeway_adj *tw_adj,
+			       enum isis_adj_usage adj_usage);
 void isis_adj_state_change(struct isis_adjacency *adj,
 			   enum isis_adj_state state, const char *reason);
 void isis_adj_print(struct isis_adjacency *adj);
diff --git a/isisd/isis_pdu.c b/isisd/isis_pdu.c
index 20a491ac18..8dd43258fd 100644
--- a/isisd/isis_pdu.c
+++ b/isisd/isis_pdu.c
@@ -120,6 +120,32 @@ struct iih_info {
 
 static int process_p2p_hello(struct iih_info *iih)
 {
+	struct isis_threeway_adj *tw_adj = iih->tlvs->threeway_adj;
+	if (tw_adj) {
+		if (tw_adj->state > ISIS_THREEWAY_DOWN) {
+			if (isis->debugs & DEBUG_ADJ_PACKETS) {
+				zlog_debug("ISIS-Adj (%s): Rcvd P2P IIH from (%s) with invalid three-way state: %d\n",
+					   iih->circuit->area->area_tag,
+					   iih->circuit->interface->name,
+					   tw_adj->state);
+			}
+			return ISIS_WARNING;
+		}
+
+		if (tw_adj->neighbor_set
+		    && (memcmp(tw_adj->neighbor_id, isis->sysid, ISIS_SYS_ID_LEN)
+			|| tw_adj->neighbor_circuit_id != (uint32_t) iih->circuit->idx)) {
+
+			if (isis->debugs & DEBUG_ADJ_PACKETS) {
+				zlog_debug("ISIS-Adj (%s): Rcvd P2P IIH from (%s) which lists IS/Circuit different from us as neighbor.\n",
+					   iih->circuit->area->area_tag,
+					   iih->circuit->interface->name);
+			}
+
+			return ISIS_WARNING;
+		}
+	}
+
 	/*
 	 * My interpertation of the ISO, if no adj exists we will create one for
 	 * the circuit
@@ -155,6 +181,9 @@ static int process_p2p_hello(struct iih_info *iih)
 		adj->sys_type = ISIS_SYSTYPE_UNKNOWN;
 	}
 
+	if (tw_adj && adj->threeway_state == ISIS_THREEWAY_DOWN)
+		adj->ext_circuit_id = tw_adj->local_circuit_id;
+
 	/* 8.2.6 Monitoring point-to-point adjacencies */
 	adj->hold_time = iih->holdtime;
 	adj->last_upd = time(NULL);
@@ -183,14 +212,10 @@ static int process_p2p_hello(struct iih_info *iih)
 			switch (iih->circ_type) {
 			case IS_LEVEL_1:
 			case IS_LEVEL_1_AND_2:
-				if (adj->adj_state != ISIS_ADJ_UP) {
-					/* (4) adj state up */
-					isis_adj_state_change(adj, ISIS_ADJ_UP,
-							      NULL);
-					/* (5) adj usage level 1 */
-					adj->adj_usage = ISIS_ADJ_LEVEL1;
-				} else if (adj->adj_usage == ISIS_ADJ_LEVEL1) {
-					; /* accept */
+				if (adj->adj_state != ISIS_ADJ_UP
+				    || adj->adj_usage == ISIS_ADJ_LEVEL1) {
+					isis_adj_process_threeway(adj, tw_adj,
+								  ISIS_ADJ_LEVEL1);
 				}
 				break;
 			case IS_LEVEL_2:
@@ -213,14 +238,10 @@ static int process_p2p_hello(struct iih_info *iih)
 		if (iih->circuit->area->is_type == IS_LEVEL_1_AND_2) {
 			switch (iih->circ_type) {
 			case IS_LEVEL_1:
-				if (adj->adj_state != ISIS_ADJ_UP) {
-					/* (6) adj state up */
-					isis_adj_state_change(adj, ISIS_ADJ_UP,
-							      NULL);
-					/* (7) adj usage level 1 */
-					adj->adj_usage = ISIS_ADJ_LEVEL1;
-				} else if (adj->adj_usage == ISIS_ADJ_LEVEL1) {
-					; /* accept */
+				if (adj->adj_state != ISIS_ADJ_UP
+				    || adj->adj_usage == ISIS_ADJ_LEVEL1) {
+					isis_adj_process_threeway(adj, tw_adj,
+								  ISIS_ADJ_LEVEL1);
 				} else if ((adj->adj_usage
 					    == ISIS_ADJ_LEVEL1AND2)
 					   || (adj->adj_usage
@@ -232,12 +253,10 @@ static int process_p2p_hello(struct iih_info *iih)
 				}
 				break;
 			case IS_LEVEL_2:
-				if (adj->adj_state != ISIS_ADJ_UP) {
-					/* (6) adj state up */
-					isis_adj_state_change(adj, ISIS_ADJ_UP,
-							      NULL);
-					/* (9) adj usage level 2 */
-					adj->adj_usage = ISIS_ADJ_LEVEL2;
+				if (adj->adj_state != ISIS_ADJ_UP
+				    || adj->adj_usage == ISIS_ADJ_LEVEL2) {
+					isis_adj_process_threeway(adj, tw_adj,
+								  ISIS_ADJ_LEVEL2);
 				} else if ((adj->adj_usage == ISIS_ADJ_LEVEL1)
 					   || (adj->adj_usage
 					       == ISIS_ADJ_LEVEL1AND2)) {
@@ -245,17 +264,13 @@ static int process_p2p_hello(struct iih_info *iih)
 					isis_adj_state_change(adj,
 							      ISIS_ADJ_DOWN,
 							      "Wrong System");
-				} else if (adj->adj_usage == ISIS_ADJ_LEVEL2) {
-					; /* Accept */
 				}
 				break;
 			case IS_LEVEL_1_AND_2:
-				if (adj->adj_state != ISIS_ADJ_UP) {
-					/* (6) adj state up */
-					isis_adj_state_change(adj, ISIS_ADJ_UP,
-							      NULL);
-					/* (10) adj usage level 1 */
-					adj->adj_usage = ISIS_ADJ_LEVEL1AND2;
+				if (adj->adj_state != ISIS_ADJ_UP
+				    || adj->adj_usage == ISIS_ADJ_LEVEL1AND2) {
+					isis_adj_process_threeway(adj, tw_adj,
+								  ISIS_ADJ_LEVEL1AND2);
 				} else if ((adj->adj_usage == ISIS_ADJ_LEVEL1)
 					   || (adj->adj_usage
 					       == ISIS_ADJ_LEVEL2)) {
@@ -263,9 +278,6 @@ static int process_p2p_hello(struct iih_info *iih)
 					isis_adj_state_change(adj,
 							      ISIS_ADJ_DOWN,
 							      "Wrong System");
-				} else if (adj->adj_usage
-					   == ISIS_ADJ_LEVEL1AND2) {
-					; /* Accept */
 				}
 				break;
 			}
@@ -292,20 +304,16 @@ static int process_p2p_hello(struct iih_info *iih)
 				break;
 			case IS_LEVEL_1_AND_2:
 			case IS_LEVEL_2:
-				if (adj->adj_state != ISIS_ADJ_UP) {
-					/* (7) adj state up */
-					isis_adj_state_change(adj, ISIS_ADJ_UP,
-							      NULL);
-					/* (8) adj usage level 2 */
-					adj->adj_usage = ISIS_ADJ_LEVEL2;
+				if (adj->adj_state != ISIS_ADJ_UP
+				    || adj->adj_usage == ISIS_ADJ_LEVEL2) {
+					isis_adj_process_threeway(adj, tw_adj,
+								  ISIS_ADJ_LEVEL2);
 				} else if (adj->adj_usage
 					   == ISIS_ADJ_LEVEL1AND2) {
 					/* (6) down - wrong system */
 					isis_adj_state_change(adj,
 							      ISIS_ADJ_DOWN,
 							      "Wrong System");
-				} else if (adj->adj_usage == ISIS_ADJ_LEVEL2) {
-					; /* Accept */
 				}
 				break;
 			}
@@ -350,12 +358,10 @@ static int process_p2p_hello(struct iih_info *iih)
 				break;
 			case IS_LEVEL_1_AND_2:
 			case IS_LEVEL_2:
-				if (adj->adj_state != ISIS_ADJ_UP) {
-					/* (8) adj state up */
-					isis_adj_state_change(adj, ISIS_ADJ_UP,
-							      NULL);
-					/* (9) adj usage level 2 */
-					adj->adj_usage = ISIS_ADJ_LEVEL2;
+				if (adj->adj_state != ISIS_ADJ_UP
+				    || adj->adj_usage == ISIS_ADJ_LEVEL2) {
+					isis_adj_process_threeway(adj, tw_adj,
+								  ISIS_ADJ_LEVEL2);
 				} else if (adj->adj_usage == ISIS_ADJ_LEVEL1) {
 					/* (7) down - wrong system */
 					isis_adj_state_change(adj,
@@ -374,8 +380,6 @@ static int process_p2p_hello(struct iih_info *iih)
 							adj, ISIS_ADJ_DOWN,
 							"Area Mismatch");
 					}
-				} else if (adj->adj_usage == ISIS_ADJ_LEVEL2) {
-					; /* Accept */
 				}
 				break;
 			}
@@ -1552,9 +1556,24 @@ int send_hello(struct isis_circuit *circuit, int level)
 
 	isis_tlvs_add_area_addresses(tlvs, circuit->area->area_addrs);
 
-	if (circuit->circ_type == CIRCUIT_T_BROADCAST)
+	if (circuit->circ_type == CIRCUIT_T_BROADCAST) {
 		isis_tlvs_add_lan_neighbors(
 			tlvs, circuit->u.bc.lan_neighs[level - 1]);
+	} else if (circuit->circ_type == CIRCUIT_T_P2P) {
+		uint32_t ext_circuit_id = circuit->idx;
+		if (circuit->u.p2p.neighbor) {
+			isis_tlvs_add_threeway_adj(tlvs,
+					circuit->u.p2p.neighbor->threeway_state,
+					ext_circuit_id,
+					circuit->u.p2p.neighbor->sysid,
+					circuit->u.p2p.neighbor->ext_circuit_id);
+		} else {
+			isis_tlvs_add_threeway_adj(tlvs,
+					ISIS_THREEWAY_DOWN,
+					ext_circuit_id,
+					NULL, 0);
+		}
+	}
 
 	isis_tlvs_set_protocols_supported(tlvs, &circuit->nlpids);