diff --git a/nova/exception.py b/nova/exception.py
index 1204fd4c8c..4f072d81d0 100644
--- a/nova/exception.py
+++ b/nova/exception.py
@@ -880,6 +880,11 @@ class PortBindingDeletionFailed(NovaException):
                 "%(host)s.")
 
 
+class PortBindingActivationFailed(NovaException):
+    msg_fmt = _("Failed to activate binding for port %(port_id)s and host "
+                "%(host)s.")
+
+
 class PortUpdateFailed(Invalid):
     msg_fmt = _("Port update failed for port %(port_id)s: %(reason)s")
 
diff --git a/nova/network/neutronv2/api.py b/nova/network/neutronv2/api.py
index e5f55becbe..fa845f8aea 100644
--- a/nova/network/neutronv2/api.py
+++ b/nova/network/neutronv2/api.py
@@ -1284,6 +1284,44 @@ class API(base_api.NetworkAPI):
                 raise exception.PortBindingDeletionFailed(
                     port_id=port_id, host=host)
 
+    def activate_port_binding(self, context, port_id, host):
+        """Activates an inactive port binding.
+
+        If there are two port bindings to different hosts, activating the
+        inactive binding atomically changes the other binding to inactive.
+
+        :param context: The request context for the operation.
+        :param port_id: The ID of the port with an inactive binding on the
+                        host.
+        :param host: The host on which the inactive port binding should be
+                     activated.
+        :raises: nova.exception.PortBindingActivationFailed if a non-409 error
+            response is received from neutron.
+        """
+        client = _get_ksa_client(context, admin=True)
+        # This is a bit weird in that we don't PUT and update the status
+        # to ACTIVE, it's more like a POST action method in the compute API.
+        resp = client.put(
+            '/v2.0/ports/%s/bindings/%s/activate' % (port_id, host),
+            raise_exc=False)
+        if resp:
+            LOG.debug('Activated binding for port %s and host %s.',
+                      port_id, host)
+        else:
+            # A 409 means the port binding is already active, which shouldn't
+            # happen if the caller is doing things in the correct order.
+            if resp.status_code == 409:
+                LOG.warning('Binding for port %s and host %s is already '
+                            'active.', port_id, host)
+            else:
+                # Log the details, raise an exception.
+                LOG.error('Unexpected error trying to activate binding '
+                          'for port %s and host %s. Code: %s. '
+                          'Error: %s', port_id, host, resp.status_code,
+                          resp.text)
+                raise exception.PortBindingActivationFailed(
+                    port_id=port_id, host=host)
+
     def _get_pci_device_profile(self, pci_dev):
         dev_spec = self.pci_whitelist.get_devspec(pci_dev)
         if dev_spec:
diff --git a/nova/tests/unit/network/test_neutronv2.py b/nova/tests/unit/network/test_neutronv2.py
index 16fa258fc1..c6aca3bf10 100644
--- a/nova/tests/unit/network/test_neutronv2.py
+++ b/nova/tests/unit/network/test_neutronv2.py
@@ -5464,6 +5464,43 @@ class TestPortBindingWithMock(test.NoDBTestCase):
             else:
                 self.api.delete_port_binding(ctxt, port_id, 'fake-host')
 
+    @mock.patch('nova.network.neutronv2.api._get_ksa_client')
+    def test_activate_port_binding(self, mock_client):
+        """Tests the happy path of activating an inactive port binding."""
+        ctxt = context.get_context()
+        resp = fake_req.FakeResponse(200)
+        mock_client.return_value.put.return_value = resp
+        self.api.activate_port_binding(ctxt, uuids.port_id, 'fake-host')
+        mock_client.return_value.put.assert_called_once_with(
+            '/v2.0/ports/%s/bindings/fake-host/activate' % uuids.port_id,
+            raise_exc=False)
+
+    @mock.patch('nova.network.neutronv2.api._get_ksa_client')
+    @mock.patch('nova.network.neutronv2.api.LOG.warning')
+    def test_activate_port_binding_already_active(
+            self, mock_log_warning, mock_client):
+        """Tests the 409 case of activating an already active port binding."""
+        ctxt = context.get_context()
+        mock_client.return_value.put.return_value = fake_req.FakeResponse(409)
+        self.api.activate_port_binding(ctxt, uuids.port_id, 'fake-host')
+        mock_client.return_value.put.assert_called_once_with(
+            '/v2.0/ports/%s/bindings/fake-host/activate' % uuids.port_id,
+            raise_exc=False)
+        self.assertEqual(1, mock_log_warning.call_count)
+        self.assertIn('is already active', mock_log_warning.call_args[0][0])
+
+    @mock.patch('nova.network.neutronv2.api._get_ksa_client')
+    def test_activate_port_binding_fails(self, mock_client):
+        """Tests the unknown error case of binding activation."""
+        ctxt = context.get_context()
+        mock_client.return_value.put.return_value = fake_req.FakeResponse(500)
+        self.assertRaises(exception.PortBindingActivationFailed,
+                          self.api.activate_port_binding,
+                          ctxt, uuids.port_id, 'fake-host')
+        mock_client.return_value.put.assert_called_once_with(
+            '/v2.0/ports/%s/bindings/fake-host/activate' % uuids.port_id,
+            raise_exc=False)
+
 
 class TestAllocateForInstance(test.NoDBTestCase):
     def setUp(self):