diff --git a/neutron/common/_constants.py b/neutron/common/_constants.py
index 05dc54861ed..bb1da44e264 100644
--- a/neutron/common/_constants.py
+++ b/neutron/common/_constants.py
@@ -76,4 +76,5 @@ IDPOOL_SELECT_SIZE = 100
 # with these owners, it will allow subnet deletion to proceed with the
 # IP allocations being cleaned up by cascade.
 AUTO_DELETE_PORT_OWNERS = [constants.DEVICE_OWNER_DHCP,
-                           constants.DEVICE_OWNER_DISTRIBUTED]
+                           constants.DEVICE_OWNER_DISTRIBUTED,
+                           constants.DEVICE_OWNER_AGENT_GW]
diff --git a/neutron/db/l3_dvr_db.py b/neutron/db/l3_dvr_db.py
index f5df0244a82..140bdf3823a 100644
--- a/neutron/db/l3_dvr_db.py
+++ b/neutron/db/l3_dvr_db.py
@@ -13,6 +13,7 @@
 #    under the License.
 import collections
 
+from neutron_lib.api.definitions import external_net as extnet_apidef
 from neutron_lib.api.definitions import l3 as l3_apidef
 from neutron_lib.api.definitions import portbindings
 from neutron_lib.api.definitions import portbindings_extended
@@ -409,6 +410,15 @@ class DVRResourceOperationHandler(object):
                 if host_id:
                     return
 
+    @registry.receives(resources.NETWORK, [events.AFTER_DELETE])
+    def delete_fip_namespaces_for_ext_net(self, rtype, event, trigger,
+                                          context, network, **kwargs):
+        if network.get(extnet_apidef.EXTERNAL):
+            # Send the information to all the L3 Agent hosts
+            # to clean up the fip namespace as it is no longer required.
+            self.l3plugin.l3_rpc_notifier.delete_fipnamespace_for_ext_net(
+                context, network['id'])
+
     def _get_ports_for_allowed_address_pair_ip(self, context, network_id,
                                                fixed_ip):
         """Return all active ports associated with the allowed_addr_pair ip."""
diff --git a/neutron/tests/unit/db/test_db_base_plugin_v2.py b/neutron/tests/unit/db/test_db_base_plugin_v2.py
index 10746ffbeb7..0363d593f47 100644
--- a/neutron/tests/unit/db/test_db_base_plugin_v2.py
+++ b/neutron/tests/unit/db/test_db_base_plugin_v2.py
@@ -1611,17 +1611,25 @@ fixed_ips=ip_address%%3D%s&fixed_ips=ip_address%%3D%s&fixed_ips=subnet_id%%3D%s
             res = req.get_response(self.api)
             self.assertEqual(webob.exc.HTTPConflict.code, res.status_int)
 
-    def test_delete_network_port_exists_owned_by_network(self):
+    def _test_delete_network_port_exists_owned_by_network(self, device_owner):
         res = self._create_network(fmt=self.fmt, name='net',
                                    admin_state_up=True)
         network = self.deserialize(self.fmt, res)
         network_id = network['network']['id']
         self._create_port(self.fmt, network_id,
-                          device_owner=constants.DEVICE_OWNER_DHCP)
+                          device_owner=device_owner)
         req = self.new_delete_request('networks', network_id)
         res = req.get_response(self.api)
         self.assertEqual(webob.exc.HTTPNoContent.code, res.status_int)
 
+    def test_test_delete_network_port_exists_dhcp(self):
+        self._test_delete_network_port_exists_owned_by_network(
+            constants.DEVICE_OWNER_DHCP)
+
+    def test_test_delete_network_port_exists_fip_gw(self):
+        self._test_delete_network_port_exists_owned_by_network(
+            constants.DEVICE_OWNER_AGENT_GW)
+
     def test_delete_network_port_exists_owned_by_network_race(self):
         res = self._create_network(fmt=self.fmt, name='net',
                                    admin_state_up=True)