diff --git a/neutron/db/l3_dvr_db.py b/neutron/db/l3_dvr_db.py
index 49cce500e24..0a1bfd783e0 100644
--- a/neutron/db/l3_dvr_db.py
+++ b/neutron/db/l3_dvr_db.py
@@ -204,11 +204,11 @@ class DVRResourceOperationHandler(object):
         return ports
 
     def _add_csnat_router_interface_port(
-            self, context, router, network_id, subnet_id, do_pop=True):
+            self, context, router, network_id, subnets, do_pop=True):
         """Add SNAT interface to the specified router and subnet."""
         port_data = {'tenant_id': '',
                      'network_id': network_id,
-                     'fixed_ips': [{'subnet_id': subnet_id}],
+                     'fixed_ips': subnets,
                      'device_id': router.id,
                      'device_owner': const.DEVICE_OWNER_ROUTER_SNAT,
                      'admin_state_up': True,
@@ -253,15 +253,31 @@ class DVRResourceOperationHandler(object):
         )
         LOG.info('SNAT interface port list does not exist,'
                  ' so create one: %s', port_list)
+        v6_subnets = []
+        network = None
         for intf in int_ports:
             if intf.fixed_ips:
                 # Passing the subnet for the port to make sure the IP's
                 # are assigned on the right subnet if multiple subnet
                 # exists
-                snat_port = self._add_csnat_router_interface_port(
-                    context, router, intf['network_id'],
-                    intf['fixed_ips'][0]['subnet_id'], do_pop=False)
-                port_list.append(snat_port)
+                for fixed_ip in intf['fixed_ips']:
+                    ip_version = n_utils.get_ip_version(
+                        fixed_ip.get('ip_address'))
+                    if ip_version == const.IP_VERSION_4:
+                        snat_port = self._add_csnat_router_interface_port(
+                            context, router, intf['network_id'],
+                            [{'subnet_id': fixed_ip['subnet_id']}],
+                            do_pop=False)
+                        port_list.append(snat_port)
+                    else:
+                        v6_subnets.append(
+                            {"subnet_id": fixed_ip['subnet_id']})
+                        network = intf['network_id']
+        if v6_subnets:
+            snat_port = self._add_csnat_router_interface_port(
+                context, router, network,
+                v6_subnets, do_pop=False)
+            port_list.append(snat_port)
         if port_list:
             self.l3plugin._populate_mtu_and_subnets_for_ports(
                 context, port_list)
@@ -397,7 +413,7 @@ class DVRResourceOperationHandler(object):
         admin_context = context.elevated()
         self._add_csnat_router_interface_port(
             admin_context, router_db, port['network_id'],
-            port['fixed_ips'][-1]['subnet_id'])
+            [{'subnet_id': port['fixed_ips'][-1]['subnet_id']}])
 
     @registry.receives(resources.ROUTER_INTERFACE, [events.AFTER_CREATE])
     @db_api.retry_if_session_inactive()
diff --git a/neutron/tests/unit/db/test_l3_dvr_db.py b/neutron/tests/unit/db/test_l3_dvr_db.py
index e09af96da32..4706a2f8ac7 100644
--- a/neutron/tests/unit/db/test_l3_dvr_db.py
+++ b/neutron/tests/unit/db/test_l3_dvr_db.py
@@ -596,6 +596,72 @@ class L3DvrTestCase(test_db_base_plugin_v2.NeutronDbPluginV2TestCase):
     def test_distributed_to_ha_csnat_ports_removal(self):
         self._test_csnat_ports_removal(ha=True)
 
+    def test_update_router_gw_info_csnat_ports_add(self):
+        router_dict = {'name': 'test_router',
+                       'admin_state_up': True,
+                       'distributed': True}
+        router = self._create_router(router_dict)
+        with self.network() as net_ext,\
+                self.network() as net_int,\
+                self.subnet(
+                    network=net_int,
+                    cidr='2001:db8:1::/64',
+                    gateway_ip='2001:db8:1::1',
+                    ip_version=const.IP_VERSION_6) as v6_subnet1,\
+                self.subnet(
+                    network=net_int,
+                    cidr='2001:db8:2::/64',
+                    gateway_ip='2001:db8:2::1',
+                    ip_version=const.IP_VERSION_6) as v6_subnet2,\
+                self.subnet(
+                    network=net_int,
+                    cidr='10.10.10.0/24') as v4_subnet:
+
+            self.core_plugin.update_network(
+                self.ctx, net_ext['network']['id'],
+                {'network': {'router:external': True}})
+
+            # Add router interface, then set router gateway
+            self.mixin.add_router_interface(self.ctx, router['id'],
+                {'subnet_id': v6_subnet1['subnet']['id']})
+            self.mixin.add_router_interface(self.ctx, router['id'],
+                {'subnet_id': v6_subnet2['subnet']['id']})
+            self.mixin.add_router_interface(self.ctx, router['id'],
+                {'subnet_id': v4_subnet['subnet']['id']})
+
+            dvr_filters = {'device_owner':
+                           [const.DEVICE_OWNER_DVR_INTERFACE]}
+            dvr_ports = self.core_plugin.get_ports(
+                self.ctx, filters=dvr_filters)
+            # One for IPv4, one for two IPv6 subnets
+            self.assertEqual(2, len(dvr_ports))
+
+            self.mixin.update_router(
+                self.ctx, router['id'],
+                {'router': {'external_gateway_info':
+                            {'network_id': net_ext['network']['id']}}})
+
+            csnat_filters = {'device_owner':
+                             [const.DEVICE_OWNER_ROUTER_SNAT]}
+            csnat_ports = self.core_plugin.get_ports(
+                self.ctx, filters=csnat_filters)
+            # One for IPv4, one for two IPv6 subnets
+            self.assertEqual(2, len(csnat_ports))
+
+            # Remove v4 subnet interface from router
+            self.mixin.remove_router_interface(
+                self.ctx, router['id'],
+                {'subnet_id': v4_subnet['subnet']['id']})
+
+            dvr_ports = self.core_plugin.get_ports(
+                self.ctx, filters=dvr_filters)
+            self.assertEqual(1, len(dvr_ports))
+
+            csnat_ports = self.core_plugin.get_ports(
+                self.ctx, filters=csnat_filters)
+            self.assertEqual(1, len(csnat_ports))
+            self.assertEqual(2, len(csnat_ports[0]['fixed_ips']))
+
     def test_remove_router_interface_csnat_ports_removal(self):
         router_dict = {'name': 'test_router', 'admin_state_up': True,
                        'distributed': True}