diff --git a/neutron/extensions/auto_allocated_topology.py b/neutron/extensions/auto_allocated_topology.py
index 15162cd0e73..215b59c9569 100644
--- a/neutron/extensions/auto_allocated_topology.py
+++ b/neutron/extensions/auto_allocated_topology.py
@@ -14,69 +14,25 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-from neutron_lib.api import converters
+from neutron_lib.api.definitions import auto_allocated_topology
 from neutron_lib.api import extensions as api_extensions
 from neutron_lib.plugins import directory
 
 from neutron.api import extensions
 from neutron.api.v2 import base
 
-RESOURCE_NAME = "auto_allocated_topology"
-COLLECTION_NAME = "auto_allocated_topologies"
-IS_DEFAULT = "is_default"
-EXT_ALIAS = RESOURCE_NAME.replace('_', '-')
 
-RESOURCE_ATTRIBUTE_MAP = {
-    COLLECTION_NAME: {
-        'id': {'allow_post': False, 'allow_put': False,
-               'validate': {'type:uuid': None},
-               'is_visible': True},
-        'tenant_id': {'allow_post': False, 'allow_put': False,
-                      'validate': {'type:uuid': None},
-                      'is_visible': True},
-    },
-    'networks': {IS_DEFAULT: {'allow_post': True,
-                              'allow_put': True,
-                              'default': False,
-                              'is_visible': True,
-                              'convert_to': converters.convert_to_boolean,
-                              'enforce_policy': True,
-                              'required_by_policy': True}},
-}
-
-
-class Auto_allocated_topology(api_extensions.ExtensionDescriptor):
-
-    @classmethod
-    def get_name(cls):
-        return "Auto Allocated Topology Services"
-
-    @classmethod
-    def get_alias(cls):
-        return EXT_ALIAS
-
-    @classmethod
-    def get_description(cls):
-        return "Auto Allocated Topology Services."
-
-    @classmethod
-    def get_updated(cls):
-        return "2016-01-01T00:00:00-00:00"
+class Auto_allocated_topology(api_extensions.APIExtensionDescriptor):
+    api_definition = auto_allocated_topology
 
     @classmethod
     def get_resources(cls):
-        params = RESOURCE_ATTRIBUTE_MAP.get(COLLECTION_NAME, dict())
-        controller = base.create_resource(COLLECTION_NAME,
-                                          EXT_ALIAS,
-                                          directory.get_plugin(EXT_ALIAS),
-                                          params, allow_bulk=False)
-        return [extensions.ResourceExtension(EXT_ALIAS, controller)]
-
-    def get_required_extensions(self):
-        return ["subnet_allocation", "external-net", "router"]
-
-    def get_extended_resources(self, version):
-        if version == "2.0":
-            return RESOURCE_ATTRIBUTE_MAP
-        else:
-            return {}
+        params = auto_allocated_topology.RESOURCE_ATTRIBUTE_MAP.get(
+            auto_allocated_topology.COLLECTION_NAME, dict())
+        controller = base.create_resource(
+            auto_allocated_topology.COLLECTION_NAME,
+            auto_allocated_topology.ALIAS,
+            directory.get_plugin(auto_allocated_topology.ALIAS),
+            params, allow_bulk=False)
+        return [extensions.ResourceExtension(
+            auto_allocated_topology.ALIAS, controller)]
diff --git a/neutron/tests/tempest/api/test_auto_allocated_topology.py b/neutron/tests/tempest/api/test_auto_allocated_topology.py
index 0f0de5442e9..e7ebfa0124e 100644
--- a/neutron/tests/tempest/api/test_auto_allocated_topology.py
+++ b/neutron/tests/tempest/api/test_auto_allocated_topology.py
@@ -13,6 +13,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+from neutron_lib.api.definitions import auto_allocated_topology
 from oslo_config import cfg
 from tempest.lib import decorators
 
@@ -30,7 +31,7 @@ class TestAutoAllocatedTopology(base.BaseAdminNetworkTest):
     # all tests are added under TestAutoAllocatedTopology,
     # nothing bad should happen.
     force_tenant_isolation = True
-    required_extensions = ['auto-allocated-topology']
+    required_extensions = [auto_allocated_topology.ALIAS]
 
     @classmethod
     def resource_setup(cls):
@@ -84,7 +85,7 @@ class TestAutoAllocatedTopology(base.BaseAdminNetworkTest):
         self.assertEqual((0, 0, 0), resources_before)
 
         body = self.client.get_auto_allocated_topology()
-        topology = body['auto_allocated_topology']
+        topology = body[auto_allocated_topology.RESOURCE_NAME]
         self.assertIsNotNone(topology)
         self._add_topology_cleanup(self.client)
 
@@ -97,7 +98,7 @@ class TestAutoAllocatedTopology(base.BaseAdminNetworkTest):
         self.assertEqual((1, self.num_subnetpools, 1), resources_after1)
 
         body = self.client.get_auto_allocated_topology()
-        topology = body['auto_allocated_topology']
+        topology = body[auto_allocated_topology.RESOURCE_NAME]
         network_id2 = topology['id']
         resources_after2 = self._count_topology_resources()
         # After the initial GET, the API should be idempotent
@@ -109,7 +110,7 @@ class TestAutoAllocatedTopology(base.BaseAdminNetworkTest):
         resources_before = self._count_topology_resources()
         self.assertEqual((0, 0, 0), resources_before)
         body = self.client.get_auto_allocated_topology()
-        topology = body['auto_allocated_topology']
+        topology = body[auto_allocated_topology.RESOURCE_NAME]
         self.assertIsNotNone(topology)
         self.client.delete_auto_allocated_topology()
         resources_after = self._count_topology_resources()