diff --git a/isisd/isis_circuit.h b/isisd/isis_circuit.h
index cbe4040b64..d4c7baea1a 100644
--- a/isisd/isis_circuit.h
+++ b/isisd/isis_circuit.h
@@ -31,6 +31,7 @@
 
 #include "isis_constants.h"
 #include "isis_common.h"
+#include "isis_csm.h"
 
 DECLARE_HOOK(isis_if_new_hook, (struct interface *ifp), (ifp));
 
@@ -77,7 +78,7 @@ struct isis_circuit_arg {
 };
 
 struct isis_circuit {
-	int state;
+	enum isis_circuit_state state;
 	uint8_t circuit_id;	  /* l1/l2 bcast CircuitID */
 	time_t last_uptime;
 	struct isis *isis;
diff --git a/isisd/isis_csm.c b/isisd/isis_csm.c
index 736d8d63f9..ebb68ba3f0 100644
--- a/isisd/isis_csm.c
+++ b/isisd/isis_csm.c
@@ -60,12 +60,14 @@ static const char *const csm_eventstr[] = {
 
 #define EVENT2STR(E) csm_eventstr[E]
 
-struct isis_circuit *
-isis_csm_state_change(int event, struct isis_circuit *circuit, void *arg)
+struct isis_circuit *isis_csm_state_change(enum isis_circuit_event event,
+					   struct isis_circuit *circuit,
+					   void *arg)
 {
-	int old_state;
+	enum isis_circuit_state old_state;
 	struct isis *isis = NULL;
 	struct isis_area *area = NULL;
+	struct interface *ifp;
 
 	old_state = circuit ? circuit->state : C_STATE_NA;
 	if (IS_DEBUG_EVENTS)
@@ -85,23 +87,29 @@ isis_csm_state_change(int event, struct isis_circuit *circuit, void *arg)
 			circuit->state = C_STATE_CONF;
 			break;
 		case IF_UP_FROM_Z:
-			isis = isis_lookup_by_vrfid(((struct interface *)arg)->vrf_id);
+			ifp = arg;
+			isis = isis_lookup_by_vrfid(ifp->vrf_id);
 			if (isis == NULL) {
-				zlog_warn(
-					" %s : ISIS routing instance not found",
-					__func__);
+				if (IS_DEBUG_EVENTS)
+					zlog_debug(
+						" %s : ISIS routing instance not found when attempting to apply against interface %s",
+						__func__, ifp->name);
 				break;
 			}
 			circuit = isis_circuit_new(isis);
-			isis_circuit_if_add(circuit, (struct interface *)arg);
+			isis_circuit_if_add(circuit, ifp);
 			listnode_add(isis->init_circ_list, circuit);
 			circuit->state = C_STATE_INIT;
 			break;
 		case ISIS_DISABLE:
-			zlog_warn("circuit already disabled");
+			if (IS_DEBUG_EVENTS)
+				zlog_debug(
+					"circuit disable event passed for a non existent circuit");
 			break;
 		case IF_DOWN_FROM_Z:
-			zlog_warn("circuit already disconnected");
+			if (IS_DEBUG_EVENTS)
+				zlog_debug(
+					"circuit disconnect event passed for a non existent circuit");
 			break;
 		}
 		break;
@@ -123,11 +131,14 @@ isis_csm_state_change(int event, struct isis_circuit *circuit, void *arg)
 					circuit);
 			break;
 		case IF_UP_FROM_Z:
-			assert(circuit);
-			zlog_warn("circuit already connected");
+			if (IS_DEBUG_EVENTS)
+				zlog_debug("circuit %s already connected",
+					   circuit->interface->name);
 			break;
 		case ISIS_DISABLE:
-			zlog_warn("circuit already disabled");
+			if (IS_DEBUG_EVENTS)
+				zlog_debug("circuit %s already disabled",
+					   circuit->interface->name);
 			break;
 		case IF_DOWN_FROM_Z:
 			isis_circuit_if_del(circuit, (struct interface *)arg);
@@ -142,7 +153,9 @@ isis_csm_state_change(int event, struct isis_circuit *circuit, void *arg)
 		assert(circuit);
 		switch (event) {
 		case ISIS_ENABLE:
-			zlog_warn("circuit already enabled");
+			if (IS_DEBUG_EVENTS)
+				zlog_debug("circuit %p is already enabled",
+					   circuit);
 			break;
 		case IF_UP_FROM_Z:
 			isis_circuit_if_add(circuit, (struct interface *)arg);
@@ -165,7 +178,9 @@ isis_csm_state_change(int event, struct isis_circuit *circuit, void *arg)
 			circuit = NULL;
 			break;
 		case IF_DOWN_FROM_Z:
-			zlog_warn("circuit already disconnected");
+			if (IS_DEBUG_EVENTS)
+				zlog_debug("circuit %p already disconnected",
+					   circuit);
 			break;
 		}
 		break;
@@ -173,10 +188,14 @@ isis_csm_state_change(int event, struct isis_circuit *circuit, void *arg)
 		assert(circuit);
 		switch (event) {
 		case ISIS_ENABLE:
-			zlog_warn("circuit already configured");
+			if (IS_DEBUG_EVENTS)
+				zlog_debug("circuit %s already configured",
+					   circuit->interface->name);
 			break;
 		case IF_UP_FROM_Z:
-			zlog_warn("circuit already connected");
+			if (IS_DEBUG_EVENTS)
+				zlog_debug("circuit %s already connected",
+					   circuit->interface->name);
 			break;
 		case ISIS_DISABLE:
 			isis = circuit->isis;
@@ -197,9 +216,6 @@ isis_csm_state_change(int event, struct isis_circuit *circuit, void *arg)
 			break;
 		}
 		break;
-
-	default:
-		zlog_warn("Invalid circuit state %d", old_state);
 	}
 
 	if (IS_DEBUG_EVENTS)
diff --git a/isisd/isis_csm.h b/isisd/isis_csm.h
index 53a5f9d5d0..ad72ff5113 100644
--- a/isisd/isis_csm.h
+++ b/isisd/isis_csm.h
@@ -27,20 +27,25 @@
 /*
  * Circuit states
  */
-#define C_STATE_NA   0
-#define C_STATE_INIT 1		/* Connected to interface */
-#define C_STATE_CONF 2		/* Configured for ISIS    */
-#define C_STATE_UP   3		/* CONN | CONF            */
+enum isis_circuit_state {
+	C_STATE_NA,
+	C_STATE_INIT, /* Connected to interface */
+	C_STATE_CONF, /* Configured for ISIS    */
+	C_STATE_UP,   /* CONN | CONF            */
+};
 
 /*
  * Circuit events
  */
-#define ISIS_ENABLE    1
-#define IF_UP_FROM_Z   2
-#define ISIS_DISABLE   3
-#define IF_DOWN_FROM_Z 4
+enum isis_circuit_event {
+	ISIS_ENABLE = 1,
+	IF_UP_FROM_Z,
+	ISIS_DISABLE,
+	IF_DOWN_FROM_Z,
+};
 
-struct isis_circuit *
-isis_csm_state_change(int event, struct isis_circuit *circuit, void *arg);
+struct isis_circuit *isis_csm_state_change(enum isis_circuit_event event,
+					   struct isis_circuit *circuit,
+					   void *arg);
 
 #endif /* _ZEBRA_ISIS_CSM_H */