diff --git a/neutron/db/ipam_pluggable_backend.py b/neutron/db/ipam_pluggable_backend.py
index 2c4a72eee28..d4f758493f3 100644
--- a/neutron/db/ipam_pluggable_backend.py
+++ b/neutron/db/ipam_pluggable_backend.py
@@ -295,7 +295,7 @@ class IpamPluggableBackend(ipam_backend_mixin.IpamBackendMixin):
         try:
             subnets = self._ipam_get_subnets(
                 context, network_id=port['network_id'], host=host,
-                service_type=port.get('device_owner'))
+                service_type=port.get('device_owner'), fixed_configured=True)
         except ipam_exc.DeferIpam:
             subnets = []
 
diff --git a/neutron/tests/unit/db/test_ipam_pluggable_backend.py b/neutron/tests/unit/db/test_ipam_pluggable_backend.py
index c3c41b717c7..b49fca1086f 100644
--- a/neutron/tests/unit/db/test_ipam_pluggable_backend.py
+++ b/neutron/tests/unit/db/test_ipam_pluggable_backend.py
@@ -660,8 +660,8 @@ class TestDbBasePluginIpam(test_db_base.NeutronDbPluginV2TestCase):
                                            original_ips, new_ips, mac)
         mocks['driver'].get_address_request_factory.assert_called_once_with()
         mocks['ipam']._ipam_get_subnets.assert_called_once_with(
-            context, network_id=port_dict['network_id'], host=None,
-            service_type=port_dict['device_owner'])
+            context, network_id=port_dict['network_id'], fixed_configured=True,
+            host=None, service_type=port_dict['device_owner'])
         # Validate port_dict is passed into address_factory
         address_factory.get_request.assert_called_once_with(context,
                                                             port_dict,
diff --git a/neutron/tests/unit/extensions/test_segment.py b/neutron/tests/unit/extensions/test_segment.py
index 55e8378c411..bcf8b3cd21a 100644
--- a/neutron/tests/unit/extensions/test_segment.py
+++ b/neutron/tests/unit/extensions/test_segment.py
@@ -1020,8 +1020,8 @@ class TestSegmentAwareIpam(SegmentAwareIpamTestCase):
         self.assertEqual(segment_exc.HostConnectedToMultipleSegments.__name__,
                          res['NeutronError']['type'])
 
-    def test_port_update_excludes_hosts_on_segments(self):
-        """No binding information is provided, subnets on segments"""
+    def test_port_update_with_fixed_ips_ok_if_no_binding_host(self):
+        """No binding host information is provided, subnets on segments"""
         with self.network() as network:
             segment = self._test_create_segment(
                 network_id=network['network']['id'],
@@ -1041,7 +1041,33 @@ class TestSegmentAwareIpam(SegmentAwareIpamTestCase):
             port_req = self.new_update_request('ports', data, port_id)
             response = port_req.get_response(self.api)
 
-        # Gets bad request because there are no eligible subnets.
+        # The IP is allocated since there is no binding host info any
+        # subnet can be used for allocation.
+        self.assertEqual(webob.exc.HTTPOk.code, response.status_int)
+
+    def test_port_update_with_fixed_ips_fail_if_host_not_on_segment(self):
+        """Binding information is provided, subnets on segments. Update to
+        subnet on different segment fails.
+        """
+        network, segments, subnets = self._create_test_segments_with_subnets(2)
+
+        # Setup host mappings
+        self._setup_host_mappings([(segments[0]['segment']['id'], 'fakehost')])
+
+        # Create a port and validate immediate ip allocation
+        res = self._create_port_and_show(network,
+                                         arg_list=(portbindings.HOST_ID,),
+                                         **{portbindings.HOST_ID: 'fakehost'})
+        self._validate_immediate_ip_allocation(res['port']['id'])
+
+        # Try requesting an new IP, but the subnet does not match host segment
+        port_id = res['port']['id']
+        data = {'port': {
+            'fixed_ips': [{'subnet_id': subnets[1]['subnet']['id']}]}}
+        port_req = self.new_update_request('ports', data, port_id)
+        response = port_req.get_response(self.api)
+
+        # Port update fails.
         self.assertEqual(webob.exc.HTTPBadRequest.code, response.status_int)
 
     def _create_port_and_show(self, network, **kwargs):
diff --git a/releasenotes/notes/fix-update-port-fixed-ips-on-routed-provider-networks-c54a54844d9a3926.yaml b/releasenotes/notes/fix-update-port-fixed-ips-on-routed-provider-networks-c54a54844d9a3926.yaml
new file mode 100644
index 00000000000..a0320ed7ba0
--- /dev/null
+++ b/releasenotes/notes/fix-update-port-fixed-ips-on-routed-provider-networks-c54a54844d9a3926.yaml
@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    When updating the fixed-ips of a port residing on a routed provider
+    network the port update would always fail if *host* was not set.
+    See bug: `1844124 <https://bugs.launchpad.net/tripleo/+bug/1844124>`_.
+