diff --git a/neutron_tempest_plugin/api/base.py b/neutron_tempest_plugin/api/base.py
index c4bc71d..b200761 100644
--- a/neutron_tempest_plugin/api/base.py
+++ b/neutron_tempest_plugin/api/base.py
@@ -431,6 +431,8 @@
                 ip_version=ip_version, cidr=cidr, mask_bits=mask_bits):
             if gateway is not None:
                 kwargs['gateway_ip'] = str(gateway or (subnet_cidr.ip + 1))
+            else:
+                kwargs['gateway_ip'] = None
             try:
                 body = client.create_subnet(
                     network_id=network['id'],
@@ -611,7 +613,11 @@
                                cls.external_network_id)
 
         if port:
-            kwargs['port_id'] = port['id']
+            port_id = kwargs.setdefault('port_id', port['id'])
+            if port_id != port['id']:
+                message = "Port ID specified twice: {!s} != {!s}".format(
+                    port_id, port['id'])
+                raise ValueError(message)
 
         fip = client.create_floatingip(external_network_id,
                                        **kwargs)['floatingip']
diff --git a/neutron_tempest_plugin/api/test_availability_zones.py b/neutron_tempest_plugin/api/test_availability_zones.py
new file mode 100644
index 0000000..9d75c28
--- /dev/null
+++ b/neutron_tempest_plugin/api/test_availability_zones.py
@@ -0,0 +1,30 @@
+# Copyright 2018 AT&T Corporation.
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+from tempest.common import utils
+from tempest.lib import decorators
+
+from neutron_tempest_plugin.api import base
+
+
+class ListAvailableZonesTest(base.BaseNetworkTest):
+
+    @decorators.idempotent_id('5a8a8a1a-c265-11e8-a611-080027758b73')
+    @utils.requires_ext(extension="availability_zone",
+                        service="network")
+    def test_list_available_zones(self):
+        body = self.client.list_availability_zones()
+        self.assertIsNotNone(body)
+        self.assertIsInstance(body['availability_zones'], list)
diff --git a/neutron_tempest_plugin/services/network/json/network_client.py b/neutron_tempest_plugin/services/network/json/network_client.py
index 58dfbf4..3b07e24 100644
--- a/neutron_tempest_plugin/services/network/json/network_client.py
+++ b/neutron_tempest_plugin/services/network/json/network_client.py
@@ -41,7 +41,7 @@
 
         # The following list represents resource names that do not require
         # changing underscore to a hyphen
-        hyphen_exceptions = ["service_profiles"]
+        hyphen_exceptions = ["service_profiles", "availability_zones"]
         # the following map is used to construct proper URI
         # for the given neutron resource
         service_resource_prefix_map = {