diff --git a/ci/roles/router/tasks/main.yml b/ci/roles/router/tasks/main.yml
index 10f605b5..53694852 100644
--- a/ci/roles/router/tasks/main.yml
+++ b/ci/roles/router/tasks/main.yml
@@ -558,6 +558,46 @@
   assert:
     that: router is not changed
 
+- name: Create router without explicit IP address
+  openstack.cloud.router:
+     cloud: "{{ cloud }}"
+     state: present
+     name: "{{ router_name }}"
+     enable_snat: false
+     interfaces:
+         - shade_subnet1
+     network: "{{ external_network_name }}"
+     external_fixed_ips:
+        - subnet_id: shade_subnet5
+  register: router
+
+- name: Assert idempotent module
+  assert:
+    that: router is changed
+
+- name: Update router without explicit IP address
+  openstack.cloud.router:
+     cloud: "{{ cloud }}"
+     state: present
+     name: "{{ router_name }}"
+     enable_snat: false
+     interfaces:
+         - shade_subnet1
+     network: "{{ external_network_name }}"
+     external_fixed_ips:
+        - subnet_id: shade_subnet5
+  register: router
+
+- name: Assert idempotent module
+  assert:
+    that: router is not changed
+
+- name: Delete router
+  openstack.cloud.router:
+     cloud: "{{ cloud }}"
+     state: absent
+     name: "{{ router_name }}"
+
 - name: Create router with simple interface
   openstack.cloud.router:
      cloud: "{{ cloud }}"
diff --git a/plugins/modules/router.py b/plugins/modules/router.py
index a90a1472..47df8c97 100644
--- a/plugins/modules/router.py
+++ b/plugins/modules/router.py
@@ -372,6 +372,10 @@ class RouterModule(OpenStackModule):
             for p in external_fixed_ips:
                 if 'ip_address' in p:
                     req_fip_map[p['subnet_id']].add(p['ip_address'])
+                elif p['subnet_id'] in cur_fip_map:
+                    # handle idempotence of updating with no explicit ip
+                    req_fip_map[p['subnet_id']].update(
+                        cur_fip_map[p['subnet_id']])
 
             # Check if external ip addresses need to be added
             for fip in external_fixed_ips:
@@ -464,7 +468,7 @@ class RouterModule(OpenStackModule):
                 subnet = self.conn.network.find_subnet(
                     iface['subnet_id'], ignore_missing=False, **filters)
                 fip = dict(subnet_id=subnet.id)
-                if 'ip_address' in iface:
+                if iface.get('ip_address', None) is not None:
                     fip['ip_address'] = iface['ip_address']
                 external_fixed_ips.append(fip)