diff --git a/neutron/extensions/netmtu_writable.py b/neutron/extensions/netmtu_writable.py
index 2a7641accdd..919e8377bb5 100644
--- a/neutron/extensions/netmtu_writable.py
+++ b/neutron/extensions/netmtu_writable.py
@@ -10,49 +10,11 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-from neutron_lib.api import converters
-from neutron_lib.api.definitions import network
-from neutron_lib.api.definitions import network_mtu
+from neutron_lib.api.definitions import network_mtu_writable as apidef
 from neutron_lib.api import extensions
 
 
-#TODO(ihrachys) migrate api definition to neutron-lib
-
-MTU = 'mtu'
-
-RESOURCE_ATTRIBUTE_MAP = {
-    network.COLLECTION_NAME: {
-        MTU: {'allow_post': True, 'allow_put': True, 'is_visible': True,
-              'validate': {'type:non_negative': None}, 'default': 0,
-              'convert_to': converters.convert_to_int},
-    },
-}
-
-
-class Netmtu_writable(extensions.ExtensionDescriptor):
+class Netmtu_writable(extensions.APIExtensionDescriptor):
     """Extension class supporting writable network MTU."""
 
-    @classmethod
-    def get_name(cls):
-        return 'Network MTU (writable)'
-
-    @classmethod
-    def get_alias(cls):
-        return 'net-mtu-writable'
-
-    @classmethod
-    def get_description(cls):
-        return 'Provides a writable MTU attribute for a network resource.'
-
-    @classmethod
-    def get_updated(cls):
-        return '2017-07-12T00:00:00-00:00'
-
-    def get_extended_resources(self, version):
-        if version == "2.0":
-            return RESOURCE_ATTRIBUTE_MAP
-        else:
-            return {}
-
-    def get_required_extensions(self):
-        return [network_mtu.ALIAS]
+    api_definition = apidef
diff --git a/neutron/plugins/ml2/plugin.py b/neutron/plugins/ml2/plugin.py
index 877441df2fa..6453fb137de 100644
--- a/neutron/plugins/ml2/plugin.py
+++ b/neutron/plugins/ml2/plugin.py
@@ -18,6 +18,7 @@ from neutron_lib.api.definitions import allowedaddresspairs as addr_apidef
 from neutron_lib.api.definitions import availability_zone as az_def
 from neutron_lib.api.definitions import extra_dhcp_opt as edo_ext
 from neutron_lib.api.definitions import network as net_def
+from neutron_lib.api.definitions import network_mtu_writable as mtuw_apidef
 from neutron_lib.api.definitions import port as port_def
 from neutron_lib.api.definitions import port_security as psec
 from neutron_lib.api.definitions import portbindings
@@ -79,7 +80,6 @@ from neutron.db import securitygroups_rpc_base as sg_db_rpc
 from neutron.db import segments_db
 from neutron.db import subnet_service_type_db_models as service_type_db
 from neutron.db import vlantransparent_db
-from neutron.extensions import netmtu_writable as mtu_ext
 from neutron.extensions import providernet as provider
 from neutron.extensions import vlantransparent
 from neutron.plugins.common import utils as p_utils
@@ -878,7 +878,7 @@ class Ml2Plugin(db_base_plugin_v2.NeutronDbPluginV2,
             context.session.expire(db_network)
 
             if (
-                mtu_ext.MTU in net_data or
+                mtuw_apidef.MTU in net_data or
                 # NOTE(ihrachys) mtu may be null for existing networks,
                 # calculate and update it as needed; the conditional can be
                 # removed in Queens when we populate all mtu attributes and