diff --git a/tobiko/openstack/neutron/_floating_ip.py b/tobiko/openstack/neutron/_floating_ip.py
index 12d720d69..438f0c7ef 100644
--- a/tobiko/openstack/neutron/_floating_ip.py
+++ b/tobiko/openstack/neutron/_floating_ip.py
@@ -130,9 +130,8 @@ def ensure_floating_ip(fixed_ip_address: str,
         return find_floating_ip(port=port)
     except tobiko.ObjectNotFound:
         from tobiko.openstack import stacks
-        subnet = tobiko.select(port['fixed_ips']).with_attributes(
-            ip_address=fixed_ip_address).unique['subnet_id']
-        _router.ensure_router_interface(subnet=subnet)
+        for fixed_ip in port['fixed_ips']:
+            _router.ensure_router_interface(subnet=fixed_ip['subnet_id'])
         fixture = stacks.FloatingIpStackFixture(port=port)
         return tobiko.setup_fixture(fixture).floating_ip_details
 
diff --git a/tobiko/openstack/neutron/_router.py b/tobiko/openstack/neutron/_router.py
index 19036867d..036b3e3ae 100644
--- a/tobiko/openstack/neutron/_router.py
+++ b/tobiko/openstack/neutron/_router.py
@@ -187,19 +187,28 @@ def ensure_router_interface(subnet: _subnet.SubnetIdType,
                             client: _client.NeutronClientType = None):
     if isinstance(subnet, str):
         subnet = _subnet.get_subnet(subnet=subnet, client=client)
-    if 'gateway_ip' not in subnet:
-        if router is None:
-            from tobiko.openstack import stacks
-            router = stacks.get_router_id()
-        LOG.debug("Add router interface: subnet={subnet['id']}")
-        interface = add_router_interface(router=router,
-                                         subnet=subnet,
-                                         add_cleanup=False,
-                                         client=client)
-        interface_dump = json.dumps(interface, sort_keys=True, indent=4)
-        LOG.info(f"Added router interface:\n{interface_dump}")
-        subnet = _subnet.get_subnet(subnet=subnet, client=client)
-        assert subnet['gateway_ip']
+    gateway_ip = subnet.get('gateway_ip')
+    if gateway_ip is not None:
+        try:
+            gateway_port = _port.find_port(fixed_ip=f'ip_address={gateway_ip}')
+        except _port.NoSuchPort:
+            pass
+        else:
+            if gateway_port['device_owner'] == 'network:router_interface':
+                return
+
+    if router is None:
+        from tobiko.openstack import stacks
+        router = stacks.get_router_id()
+    LOG.debug("Add router interface: subnet={subnet['id']}")
+    interface = add_router_interface(router=router,
+                                     subnet=subnet,
+                                     add_cleanup=False,
+                                     client=client)
+    interface_dump = json.dumps(interface, sort_keys=True, indent=4)
+    LOG.info(f"Added router interface:\n{interface_dump}")
+    subnet = _subnet.get_subnet(subnet=subnet, client=client)
+    assert subnet['gateway_ip']
 
 
 class NoSuchRouter(tobiko.ObjectNotFound):
diff --git a/tobiko/openstack/neutron/_subnet.py b/tobiko/openstack/neutron/_subnet.py
index 09adc2a03..a7af828c8 100644
--- a/tobiko/openstack/neutron/_subnet.py
+++ b/tobiko/openstack/neutron/_subnet.py
@@ -113,5 +113,16 @@ def find_subnet(client: _client.NeutronClientType = None,
         return default
 
 
+def update_subnet(subnet: SubnetIdType,
+                  client: _client.NeutronClientType = None,
+                  **params) -> SubnetType:
+    subnet_id = get_subnet_id(subnet)
+    try:
+        return _client.neutron_client(client).update_subnet(
+                subnet_id, body={'subnet': params})['subnet']
+    except _client.NotFound as ex:
+        raise NoSuchSubnet(id=subnet_id) from ex
+
+
 class NoSuchSubnet(tobiko.ObjectNotFound):
     message = "No such subnet found for {id!r}"
diff --git a/tobiko/openstack/stacks/neutron/floating_ip.yaml b/tobiko/openstack/stacks/neutron/floating_ip.yaml
index a21b2c333..4cb564d5e 100644
--- a/tobiko/openstack/stacks/neutron/floating_ip.yaml
+++ b/tobiko/openstack/stacks/neutron/floating_ip.yaml
@@ -25,12 +25,12 @@ parameters:
 resources:
 
   _network:
-    type: OS::Neutron::Network
-    external_id: network
+    type: OS::Neutron::Net
+    external_id: {get_param: network}
 
   _port:
     type: OS::Neutron::Port
-    external_id: port
+    external_id: {get_param: port}
 
   _floating_ip:
     type: OS::Neutron::FloatingIP
@@ -55,3 +55,7 @@ outputs:
 
   port_id:
     value: {get_resource: _port}
+
+  floating_ip_id:
+    description: floating IP identifier
+    value: { get_resource: _floating_ip }