diff --git a/lib/if.c b/lib/if.c
index d4d9c4a5a4..cc964106d0 100644
--- a/lib/if.c
+++ b/lib/if.c
@@ -582,23 +582,39 @@ struct interface *if_get_by_ifindex(ifindex_t ifindex, vrf_id_t vrf_id)
 	return NULL;
 }
 
-void if_set_index(struct interface *ifp, ifindex_t ifindex)
+int if_set_index(struct interface *ifp, ifindex_t ifindex)
 {
 	struct vrf *vrf;
 
+	if (ifp->ifindex == ifindex)
+		return 0;
+
 	vrf = vrf_get(ifp->vrf_id, NULL);
 	assert(vrf);
 
-	if (ifp->ifindex == ifindex)
-		return;
+	/*
+	 * If there is already an interface with this ifindex, we will collide
+	 * on insertion, so don't even try.
+	 */
+	if (if_lookup_by_ifindex(ifindex, ifp->vrf_id))
+		return -1;
 
 	if (ifp->ifindex != IFINDEX_INTERNAL)
 		IFINDEX_RB_REMOVE(vrf, ifp);
 
 	ifp->ifindex = ifindex;
 
-	if (ifp->ifindex != IFINDEX_INTERNAL)
-		IFINDEX_RB_INSERT(vrf, ifp)
+	if (ifp->ifindex != IFINDEX_INTERNAL) {
+		/*
+		 * This should never happen, since we checked if there was
+		 * already an interface with the desired ifindex at the top of
+		 * the function. Nevertheless.
+		 */
+		if (IFINDEX_RB_INSERT(vrf, ifp))
+			return -1;
+	}
+
+	return 0;
 }
 
 void if_set_name(struct interface *ifp, const char *name)
diff --git a/lib/if.h b/lib/if.h
index 4ca2e79572..ac8d8e70ba 100644
--- a/lib/if.h
+++ b/lib/if.h
@@ -308,33 +308,58 @@ RB_HEAD(if_index_head, interface);
 RB_PROTOTYPE(if_index_head, interface, index_entry, if_cmp_index_func)
 DECLARE_QOBJ_TYPE(interface)
 
-#define IFNAME_RB_INSERT(vrf, ifp)                                             \
-	if (RB_INSERT(if_name_head, &vrf->ifaces_by_name, (ifp)))              \
-		flog_err(EC_LIB_INTERFACE,                                     \
-			 "%s(%s): corruption detected -- interface with this " \
-			 "name exists already in VRF %u!",                     \
-			 __func__, (ifp)->name, (ifp)->vrf_id);
+#define IFNAME_RB_INSERT(vrf, ifp)                                                    \
+	({                                                                            \
+		struct interface *_iz =                                               \
+			RB_INSERT(if_name_head, &vrf->ifaces_by_name, (ifp));         \
+		if (_iz)                                                              \
+			flog_err(                                                     \
+				EC_LIB_INTERFACE,                                     \
+				"%s(%s): corruption detected -- interface with this " \
+				"name exists already in VRF %u!",                     \
+				__func__, (ifp)->name, (ifp)->vrf_id);                \
+		_iz;                                                                  \
+	})
 
-#define IFNAME_RB_REMOVE(vrf, ifp)                                             \
-	if (RB_REMOVE(if_name_head, &vrf->ifaces_by_name, (ifp)) == NULL)      \
-		flog_err(EC_LIB_INTERFACE,                                     \
-			 "%s(%s): corruption detected -- interface with this " \
-			 "name doesn't exist in VRF %u!",                      \
-			 __func__, (ifp)->name, (ifp)->vrf_id);
+#define IFNAME_RB_REMOVE(vrf, ifp)                                                    \
+	({                                                                            \
+		struct interface *_iz =                                               \
+			RB_REMOVE(if_name_head, &vrf->ifaces_by_name, (ifp));         \
+		if (_iz == NULL)                                                      \
+			flog_err(                                                     \
+				EC_LIB_INTERFACE,                                     \
+				"%s(%s): corruption detected -- interface with this " \
+				"name doesn't exist in VRF %u!",                      \
+				__func__, (ifp)->name, (ifp)->vrf_id);                \
+		_iz;                                                                  \
+	})
 
-#define IFINDEX_RB_INSERT(vrf, ifp)                                            \
-	if (RB_INSERT(if_index_head, &vrf->ifaces_by_index, (ifp)))            \
-		flog_err(EC_LIB_INTERFACE,                                     \
-			 "%s(%u): corruption detected -- interface with this " \
-			 "ifindex exists already in VRF %u!",                  \
-			 __func__, (ifp)->ifindex, (ifp)->vrf_id);
 
-#define IFINDEX_RB_REMOVE(vrf, ifp)                                            \
-	if (RB_REMOVE(if_index_head, &vrf->ifaces_by_index, (ifp)) == NULL)    \
-		flog_err(EC_LIB_INTERFACE,                                     \
-			 "%s(%u): corruption detected -- interface with this " \
-			 "ifindex doesn't exist in VRF %u!",                   \
-			 __func__, (ifp)->ifindex, (ifp)->vrf_id);
+#define IFINDEX_RB_INSERT(vrf, ifp)                                                   \
+	({                                                                            \
+		struct interface *_iz = RB_INSERT(                                    \
+			if_index_head, &vrf->ifaces_by_index, (ifp));                 \
+		if (_iz)                                                              \
+			flog_err(                                                     \
+				EC_LIB_INTERFACE,                                     \
+				"%s(%u): corruption detected -- interface with this " \
+				"ifindex exists already in VRF %u!",                  \
+				__func__, (ifp)->ifindex, (ifp)->vrf_id);             \
+		_iz;                                                                  \
+	})
+
+#define IFINDEX_RB_REMOVE(vrf, ifp)                                                   \
+	({                                                                            \
+		struct interface *_iz = RB_REMOVE(                                    \
+			if_index_head, &vrf->ifaces_by_index, (ifp));                 \
+		if (_iz == NULL)                                                      \
+			flog_err(                                                     \
+				EC_LIB_INTERFACE,                                     \
+				"%s(%u): corruption detected -- interface with this " \
+				"ifindex doesn't exist in VRF %u!",                   \
+				__func__, (ifp)->ifindex, (ifp)->vrf_id);             \
+		_iz;                                                                  \
+	})
 
 #define FOR_ALL_INTERFACES(vrf, ifp)                                           \
 	if (vrf)                                                               \
@@ -502,7 +527,7 @@ extern struct interface *if_get_by_name(const char *ifname, vrf_id_t vrf_id);
 extern struct interface *if_get_by_ifindex(ifindex_t ifindex, vrf_id_t vrf_id);
 
 /* Sets the index and adds to index list */
-extern void if_set_index(struct interface *ifp, ifindex_t ifindex);
+extern int if_set_index(struct interface *ifp, ifindex_t ifindex);
 /* Sets the name and adds to name list */
 extern void if_set_name(struct interface *ifp, const char *name);