diff --git a/neutron/db/l3_db.py b/neutron/db/l3_db.py
index bd7421b98ea..b488eea83c3 100644
--- a/neutron/db/l3_db.py
+++ b/neutron/db/l3_db.py
@@ -368,17 +368,18 @@ class L3_NAT_dbonly_mixin(l3.RouterPluginBase,
         if not gw_port['fixed_ips']:
             LOG.debug('No IPs available for external network %s',
                       network_id)
-
-        with context.session.begin(subtransactions=True):
-            router.gw_port = self._core_plugin._get_port(context.elevated(),
-                                                         gw_port['id'])
-            router_port = RouterPort(
-                router_id=router.id,
-                port_id=gw_port['id'],
-                port_type=DEVICE_OWNER_ROUTER_GW
-            )
-            context.session.add(router)
-            context.session.add(router_port)
+        with p_utils.delete_port_on_error(self._core_plugin,
+                                          context.elevated(), gw_port['id']):
+            with context.session.begin(subtransactions=True):
+                router.gw_port = self._core_plugin._get_port(
+                    context.elevated(), gw_port['id'])
+                router_port = RouterPort(
+                    router_id=router.id,
+                    port_id=gw_port['id'],
+                    port_type=DEVICE_OWNER_ROUTER_GW
+                )
+                context.session.add(router)
+                context.session.add(router_port)
 
     def _validate_gw_info(self, context, gw_port, info, ext_ips):
         network_id = info['network_id'] if info else None
@@ -746,6 +747,7 @@ class L3_NAT_dbonly_mixin(l3.RouterPluginBase,
 
         # This should be True unless adding an IPv6 prefix to an existing port
         new_port = True
+        cleanup_port = False
 
         if add_by_port:
             port, subnets = self._add_interface_by_port(
@@ -755,15 +757,19 @@ class L3_NAT_dbonly_mixin(l3.RouterPluginBase,
         else:
             port, subnets, new_port = self._add_interface_by_subnet(
                     context, router, interface_info['subnet_id'], device_owner)
+            cleanup_port = new_port  # only cleanup port we created
 
         if new_port:
-            with context.session.begin(subtransactions=True):
-                router_port = RouterPort(
-                    port_id=port['id'],
-                    router_id=router.id,
-                    port_type=device_owner
-                )
-                context.session.add(router_port)
+            with p_utils.delete_port_on_error(self._core_plugin,
+                                              context, port['id']) as delmgr:
+                delmgr.delete_on_error = cleanup_port
+                with context.session.begin(subtransactions=True):
+                    router_port = RouterPort(
+                        port_id=port['id'],
+                        router_id=router.id,
+                        port_type=device_owner
+                    )
+                    context.session.add(router_port)
 
         gw_ips = []
         gw_network_id = None
diff --git a/neutron/db/l3_dvr_db.py b/neutron/db/l3_dvr_db.py
index e55be908eb7..2cc082fd716 100644
--- a/neutron/db/l3_dvr_db.py
+++ b/neutron/db/l3_dvr_db.py
@@ -307,6 +307,7 @@ class L3_NAT_with_dvr_db_mixin(l3_db.L3_NAT_db_mixin,
 
         # This should be True unless adding an IPv6 prefix to an existing port
         new_port = True
+        cleanup_port = False
 
         if add_by_port:
             port, subnets = self._add_interface_by_port(
@@ -314,31 +315,27 @@ class L3_NAT_with_dvr_db_mixin(l3_db.L3_NAT_db_mixin,
         elif add_by_sub:
             port, subnets, new_port = self._add_interface_by_subnet(
                     context, router, interface_info['subnet_id'], device_owner)
+            cleanup_port = new_port
 
         subnet = subnets[0]
 
         if new_port:
-            if router.extra_attributes.distributed and router.gw_port:
-                try:
+            with p_utils.delete_port_on_error(self._core_plugin,
+                                              context, port['id']) as delmgr:
+                if router.extra_attributes.distributed and router.gw_port:
                     admin_context = context.elevated()
                     self._add_csnat_router_interface_port(
                         admin_context, router, port['network_id'],
                         port['fixed_ips'][-1]['subnet_id'])
-                except Exception:
-                    with excutils.save_and_reraise_exception():
-                        # we need to preserve the original state prior
-                        # the request by rolling back the port creation
-                        # that led to new_port=True
-                        self._core_plugin.delete_port(
-                            admin_context, port['id'], l3_port_check=False)
 
-            with context.session.begin(subtransactions=True):
-                router_port = l3_db.RouterPort(
-                    port_id=port['id'],
-                    router_id=router.id,
-                    port_type=device_owner
-                )
-                context.session.add(router_port)
+                delmgr.delete_on_error = cleanup_port
+                with context.session.begin(subtransactions=True):
+                    router_port = l3_db.RouterPort(
+                        port_id=port['id'],
+                        router_id=router.id,
+                        port_type=device_owner
+                    )
+                    context.session.add(router_port)
 
         # NOTE: For IPv6 additional subnets added to the same
         # network we need to update the CSNAT port with respective
diff --git a/neutron/plugins/common/utils.py b/neutron/plugins/common/utils.py
index 8255b3e3632..3e6aca81cb5 100644
--- a/neutron/plugins/common/utils.py
+++ b/neutron/plugins/common/utils.py
@@ -16,6 +16,7 @@
 Common utilities and helper functions for OpenStack Networking Plugins.
 """
 
+import contextlib
 import hashlib
 
 from neutron_lib import constants as n_const
@@ -23,9 +24,10 @@ from neutron_lib import exceptions
 from oslo_config import cfg
 from oslo_log import log as logging
 from oslo_utils import encodeutils
+from oslo_utils import excutils
 import webob.exc
 
-from neutron._i18n import _, _LI
+from neutron._i18n import _, _LE, _LI
 from neutron.api.v2 import attributes
 from neutron.callbacks import events
 from neutron.callbacks import registry
@@ -195,6 +197,26 @@ def create_port(core_plugin, context, port, check_allow_post=True):
     return core_plugin.create_port(context, {'port': port_data})
 
 
+class _DelManager(object):
+    def __init__(self):
+        self.delete_on_error = True
+
+
+@contextlib.contextmanager
+def delete_port_on_error(core_plugin, context, port_id):
+    mgr = _DelManager()
+    try:
+        yield mgr
+    except Exception:
+        with excutils.save_and_reraise_exception():
+            try:
+                if mgr.delete_on_error:
+                    core_plugin.delete_port(context, port_id,
+                                            l3_port_check=False)
+            except Exception:
+                LOG.exception(_LE("Failed to cleanup port: %s"), port_id)
+
+
 def get_interface_name(name, prefix='', max_len=n_const.DEVICE_NAME_MAX_LEN):
     """Construct an interface name based on the prefix and name.
 
diff --git a/neutron/tests/unit/extensions/test_l3_ext_gw_mode.py b/neutron/tests/unit/extensions/test_l3_ext_gw_mode.py
index a6423c4da90..4298c9c7a2b 100644
--- a/neutron/tests/unit/extensions/test_l3_ext_gw_mode.py
+++ b/neutron/tests/unit/extensions/test_l3_ext_gw_mode.py
@@ -23,6 +23,7 @@ from oslo_utils import uuidutils
 import testscenarios
 from webob import exc
 
+from neutron import context as nctx
 from neutron.db import api as db_api
 from neutron.db import external_net_db
 from neutron.db import l3_db
@@ -30,6 +31,7 @@ from neutron.db import l3_gwmode_db
 from neutron.db import models_v2
 from neutron.extensions import l3
 from neutron.extensions import l3_ext_gw_mode
+from neutron import manager
 from neutron.tests import base
 from neutron.tests.unit.db import test_db_base_plugin_v2
 from neutron.tests.unit.extensions import test_l3
@@ -390,6 +392,20 @@ class ExtGwModeIntTestCase(test_db_base_plugin_v2.NeutronDbPluginV2TestCase,
                             expected_code=expected_code,
                             neutron_context=neutron_context)
 
+    def test_router_gateway_set_fail_after_port_create(self):
+        with self.router() as r, self.subnet() as s:
+            ext_net_id = s['subnet']['network_id']
+            self._set_net_external(ext_net_id)
+            plugin = manager.NeutronManager.get_plugin()
+            with mock.patch.object(plugin, '_get_port',
+                                   side_effect=ValueError()):
+                self._set_router_external_gateway(r['router']['id'],
+                                                  ext_net_id,
+                                                  expected_code=500)
+            ports = [p for p in plugin.get_ports(nctx.get_admin_context())
+                     if p['device_owner'] == l3_db.DEVICE_OWNER_ROUTER_GW]
+            self.assertFalse(ports)
+
     def test_router_gateway_set_retry(self):
         with self.router() as r, self.subnet() as s:
             ext_net_id = s['subnet']['network_id']
diff --git a/neutron/tests/unit/plugins/common/test_utils.py b/neutron/tests/unit/plugins/common/test_utils.py
index f61444192c9..16e0bde0dc0 100644
--- a/neutron/tests/unit/plugins/common/test_utils.py
+++ b/neutron/tests/unit/plugins/common/test_utils.py
@@ -16,6 +16,7 @@ import hashlib
 
 import mock
 from neutron_lib import constants
+import testtools
 
 from neutron.plugins.common import utils
 from neutron.tests import base
@@ -70,3 +71,30 @@ class TestUtils(base.BaseTestCase):
         self.assertEqual(12, len(utils.get_interface_name(LONG_NAME1,
                                                           prefix="pre-",
                                                           max_len=12)))
+
+    def test_delete_port_on_error(self):
+        core_plugin, context = mock.Mock(), mock.Mock()
+        port_id = 'pid'
+        with testtools.ExpectedException(ValueError):
+            with utils.delete_port_on_error(core_plugin, context, port_id):
+                raise ValueError()
+        core_plugin.delete_port.assert_called_once_with(context, port_id,
+                                                        l3_port_check=False)
+
+    def test_delete_port_on_error_no_delete(self):
+        core_plugin, context = mock.Mock(), mock.Mock()
+        with testtools.ExpectedException(ValueError):
+            with utils.delete_port_on_error(core_plugin, context, 1) as cm:
+                cm.delete_on_error = False
+                raise ValueError()
+        self.assertFalse(core_plugin.delete_port.called)
+
+    def test_delete_port_on_error_fail_port_delete(self):
+        core_plugin, context = mock.Mock(), mock.Mock()
+        core_plugin.delete_port.side_effect = TypeError()
+        port_id = 'pid'
+        with testtools.ExpectedException(ValueError):
+            with utils.delete_port_on_error(core_plugin, context, port_id):
+                raise ValueError()
+        core_plugin.delete_port.assert_called_once_with(context, port_id,
+                                                        l3_port_check=False)