diff --git a/daemon/core/gui/coreclient.py b/daemon/core/gui/coreclient.py
index ef50ace2..8c05a30f 100644
--- a/daemon/core/gui/coreclient.py
+++ b/daemon/core/gui/coreclient.py
@@ -283,6 +283,9 @@ class CoreClient:
             response = self.client.get_emane_config(self.session_id)
             self.emane_config = response.config
 
+            # update interface manager
+            self.interfaces_manager.joined(session.links)
+
             # draw session
             self.app.canvas.reset_and_redraw(session)
 
diff --git a/daemon/core/gui/interface.py b/daemon/core/gui/interface.py
index 3310da90..8e2f4aa6 100644
--- a/daemon/core/gui/interface.py
+++ b/daemon/core/gui/interface.py
@@ -1,5 +1,5 @@
 import logging
-from typing import TYPE_CHECKING, List, Set, Tuple, Union
+from typing import TYPE_CHECKING, Any, List, Optional, Set, Tuple
 
 import netaddr
 from netaddr import EUI, IPNetwork
@@ -13,13 +13,22 @@ if TYPE_CHECKING:
     from core.gui.graph.node import CanvasNode
 
 
+def get_index(interface: "core_pb2.Interface") -> int:
+    net = netaddr.IPNetwork(f"{interface.ip4}/{interface.ip4mask}")
+    ip_value = net.value
+    cidr_value = net.cidr.value
+    return ip_value - cidr_value
+
+
 class Subnets:
     def __init__(self, ip4: IPNetwork, ip6: IPNetwork) -> None:
         self.ip4 = ip4
         self.ip6 = ip6
         self.used_indexes = set()
 
-    def __eq__(self, other: "Subnets") -> bool:
+    def __eq__(self, other: Any) -> bool:
+        if not isinstance(other, Subnets):
+            return False
         return self.key() == other.key()
 
     def __hash__(self) -> int:
@@ -73,34 +82,55 @@ class InterfaceManager:
         self.used_subnets[subnets.key()] = subnets
         return subnets
 
-    def reset(self):
+    def reset(self) -> None:
         self.current_subnets = None
         self.used_subnets.clear()
 
-    def removed(self, links: List["core_pb2.Link"]):
+    def removed(self, links: List["core_pb2.Link"]) -> None:
         # get remaining subnets
         remaining_subnets = set()
-
-        for link in links:
+        for edge in self.app.core.links.values():
+            link = edge.link
             if link.HasField("interface_one"):
                 subnets = self.get_subnets(link.interface_one)
-                if subnets not in remaining_subnets:
-                    self.used_subnets.pop(subnets.key(), None)
+                remaining_subnets.add(subnets)
             if link.HasField("interface_two"):
                 subnets = self.get_subnets(link.interface_two)
-                if subnets not in remaining_subnets:
-                    self.used_subnets.pop(subnets.key(), None)
+                remaining_subnets.add(subnets)
 
-    def initialize_links(self, links: List["core_pb2.Link"]):
+        # remove all subnets from used subnets when no longer present
+        # or remove used indexes from subnet
+        interfaces = []
         for link in links:
             if link.HasField("interface_one"):
-                subnets = self.get_subnets(link.interface_one)
-                if subnets.key() not in self.used_subnets:
-                    self.used_subnets[subnets.key()] = subnets
+                interfaces.append(link.interface_one)
             if link.HasField("interface_two"):
-                subnets = self.get_subnets(link.interface_two)
-                if subnets.key() not in self.used_subnets:
-                    self.used_subnets[subnets.key()] = subnets
+                interfaces.append(link.interface_two)
+        for interface in interfaces:
+            subnets = self.get_subnets(interface)
+            if subnets not in remaining_subnets:
+                if self.current_subnets == subnets:
+                    self.current_subnets = None
+                self.used_subnets.pop(subnets.key(), None)
+            else:
+                index = get_index(interface)
+                subnets.used_indexes.discard(index)
+
+    def joined(self, links: List["core_pb2.Link"]) -> None:
+        interfaces = []
+        for link in links:
+            if link.HasField("interface_one"):
+                interfaces.append(link.interface_one)
+            if link.HasField("interface_two"):
+                interfaces.append(link.interface_two)
+
+        # add to used subnets and mark used indexes
+        for interface in interfaces:
+            subnets = self.get_subnets(interface)
+            index = get_index(interface)
+            subnets.used_indexes.add(index)
+            if subnets.key() not in self.used_subnets:
+                self.used_subnets[subnets.key()] = subnets
 
     def next_index(self, node: "core_pb2.Node") -> int:
         if NodeUtils.is_router_node(node):
@@ -128,7 +158,7 @@ class InterfaceManager:
 
     def determine_subnets(
         self, canvas_src_node: "CanvasNode", canvas_dst_node: "CanvasNode"
-    ):
+    ) -> None:
         src_node = canvas_src_node.core_node
         dst_node = canvas_dst_node.core_node
         is_src_container = NodeUtils.is_container_node(src_node.type)
@@ -152,7 +182,7 @@ class InterfaceManager:
 
     def find_subnets(
         self, canvas_node: "CanvasNode", visited: Set[int] = None
-    ) -> Union[IPNetwork, None]:
+    ) -> Optional[IPNetwork]:
         logging.info("finding subnet for node: %s", canvas_node.core_node.name)
         canvas = self.app.canvas
         subnets = None