diff --git a/neutron/plugins/nicira/dbexts/nicira_db.py b/neutron/plugins/nicira/dbexts/nicira_db.py
index 5fb2398f7f..10155145b9 100644
--- a/neutron/plugins/nicira/dbexts/nicira_db.py
+++ b/neutron/plugins/nicira/dbexts/nicira_db.py
@@ -18,6 +18,7 @@
 from sqlalchemy.orm import exc
 
 import neutron.db.api as db
+from neutron.openstack.common.db import exception as d_exc
 from neutron.openstack.common import log as logging
 from neutron.plugins.nicira.dbexts import nicira_models
 from neutron.plugins.nicira.dbexts import nicira_networkgw_db
@@ -49,11 +50,24 @@ def add_network_binding(session, network_id, binding_type, phy_uuid, vlan_id):
 
 def add_neutron_nsx_port_mapping(session, neutron_id,
                                  nsx_switch_id, nsx_port_id):
-    with session.begin(subtransactions=True):
+    session.begin(subtransactions=True)
+    try:
         mapping = nicira_models.NeutronNsxPortMapping(
             neutron_id, nsx_switch_id, nsx_port_id)
         session.add(mapping)
-        return mapping
+        session.commit()
+    except d_exc.DBDuplicateEntry:
+        session.rollback()
+        # do not complain if the same exact mapping is being added, otherwise
+        # re-raise because even though it is possible for the same neutron
+        # port to map to different back-end ports over time, this should not
+        # occur whilst a mapping already exists
+        current = get_nsx_switch_and_port_id(session, neutron_id)
+        if current[1] == nsx_port_id:
+            LOG.debug(_("Port mapping for %s already available"), neutron_id)
+        else:
+            raise
+    return mapping
 
 
 def get_nsx_switch_and_port_id(session, neutron_id):
diff --git a/neutron/tests/unit/nicira/test_nicira_db.py b/neutron/tests/unit/nicira/test_nicira_db.py
new file mode 100644
index 0000000000..accb6fd8e8
--- /dev/null
+++ b/neutron/tests/unit/nicira/test_nicira_db.py
@@ -0,0 +1,79 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2013 VMware, Inc.
+#
+# 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 neutron import context
+from neutron.db import api as db
+from neutron.db import models_v2
+from neutron.openstack.common.db import exception as d_exc
+from neutron.plugins.nicira.dbexts import nicira_db
+from neutron.plugins.nicira.dbexts import nicira_models
+from neutron.tests import base
+
+
+class NiciraDBTestCase(base.BaseTestCase):
+
+    def setUp(self):
+        super(NiciraDBTestCase, self).setUp()
+        db.configure_db()
+        self.ctx = context.get_admin_context()
+        self.addCleanup(db.clear_db)
+
+    def _setup_neutron_network_and_port(self, network_id, port_id):
+        with self.ctx.session.begin(subtransactions=True):
+            self.ctx.session.add(models_v2.Network(id=network_id))
+            port = models_v2.Port(id=port_id,
+                                  network_id=network_id,
+                                  mac_address='foo_mac_address',
+                                  admin_state_up=True,
+                                  status='ACTIVE',
+                                  device_id='',
+                                  device_owner='')
+            self.ctx.session.add(port)
+
+    def test_add_neutron_nsx_port_mapping_handle_duplicate_constraint(self):
+        neutron_net_id = 'foo_neutron_network_id'
+        neutron_port_id = 'foo_neutron_port_id'
+        nsx_port_id = 'foo_nsx_port_id'
+        nsx_switch_id = 'foo_nsx_switch_id'
+        self._setup_neutron_network_and_port(neutron_net_id, neutron_port_id)
+
+        nicira_db.add_neutron_nsx_port_mapping(
+            self.ctx.session, neutron_port_id, nsx_switch_id, nsx_port_id)
+        # Call the method twice to trigger a db duplicate constraint error
+        nicira_db.add_neutron_nsx_port_mapping(
+            self.ctx.session, neutron_port_id, nsx_switch_id, nsx_port_id)
+        result = (self.ctx.session.query(nicira_models.NeutronNsxPortMapping).
+                  filter_by(neutron_id=neutron_port_id).one())
+        self.assertEqual(nsx_port_id, result.nsx_port_id)
+        self.assertEqual(neutron_port_id, result.neutron_id)
+
+    def test_add_neutron_nsx_port_mapping_raise_on_duplicate_constraint(self):
+        neutron_net_id = 'foo_neutron_network_id'
+        neutron_port_id = 'foo_neutron_port_id'
+        nsx_port_id_1 = 'foo_nsx_port_id_1'
+        nsx_port_id_2 = 'foo_nsx_port_id_2'
+        nsx_switch_id = 'foo_nsx_switch_id'
+        self._setup_neutron_network_and_port(neutron_net_id, neutron_port_id)
+
+        nicira_db.add_neutron_nsx_port_mapping(
+            self.ctx.session, neutron_port_id, nsx_switch_id, nsx_port_id_1)
+        # Call the method twice to trigger a db duplicate constraint error,
+        # this time with a different nsx port id!
+        self.assertRaises(d_exc.DBDuplicateEntry,
+                          nicira_db.add_neutron_nsx_port_mapping,
+                          self.ctx.session, neutron_port_id,
+                          nsx_switch_id, nsx_port_id_2)