diff --git a/neutron_tempest_plugin/api/base_routers.py b/neutron_tempest_plugin/api/base_routers.py
index 52db742..94db116 100644
--- a/neutron_tempest_plugin/api/base_routers.py
+++ b/neutron_tempest_plugin/api/base_routers.py
@@ -31,10 +31,10 @@
             pass
 
     def _create_router(self, name, admin_state_up=False,
-                       external_network_id=None, enable_snat=None):
+                       external_network_id=None, enable_snat=None, **kwargs):
         # associate a cleanup with created routers to avoid quota limits
         router = self.create_router(name, admin_state_up,
-                                    external_network_id, enable_snat)
+                                    external_network_id, enable_snat, **kwargs)
         self.addCleanup(self._cleanup_router, router)
         return router
 
diff --git a/neutron_tempest_plugin/api/test_routers.py b/neutron_tempest_plugin/api/test_routers.py
index ff5d391..66cea78 100644
--- a/neutron_tempest_plugin/api/test_routers.py
+++ b/neutron_tempest_plugin/api/test_routers.py
@@ -326,6 +326,201 @@
                           subnet['id'], gateway_ip=None)
 
 
+class ExternalGWMultihomingRoutersTest(base_routers.BaseRouterTest):
+
+    @classmethod
+    def setUpClass(cls):
+        super().setUpClass()
+        ext_alias = 'external-gateway-multihoming'
+        try:
+            cls.client.get_extension(ext_alias)
+        except lib_exc.NotFound:
+            raise cls.skipException(f'{ext_alias} extension not available.')
+
+    @decorators.idempotent_id('33e9a156-a83f-435f-90ee-1a49dc9c350d')
+    def test_create_router_enable_default_route_ecmp(self):
+        router1 = self._create_admin_router(data_utils.rand_name('router1'),
+                                            enable_default_route_ecmp=True)
+        router2 = self._create_admin_router(data_utils.rand_name('router2'),
+                                            enable_default_route_ecmp=False)
+        self.assertEqual(router1['enable_default_route_ecmp'], True)
+        self.assertEqual(router2['enable_default_route_ecmp'], False)
+
+    @decorators.idempotent_id('bfbad985-2df2-4cd9-9c32-819b5508c40e')
+    def test_update_router_enable_default_route_ecmp(self):
+        router = self._create_router(data_utils.rand_name('router'))
+        updated_router = self.admin_client.update_router(
+            router['id'],
+            enable_default_route_ecmp=not router['enable_default_route_ecmp'])
+        self.assertNotEqual(
+            router['enable_default_route_ecmp'],
+            updated_router['router']['enable_default_route_ecmp'])
+
+    @decorators.idempotent_id('a22016a6-f118-4eb5-abab-7e241ae01848')
+    def test_update_router_enable_default_route_bfd(self):
+        router = self._create_router(data_utils.rand_name('router'))
+        updated_router = self.admin_client.update_router(
+            router['id'],
+            enable_default_route_bfd=not router['enable_default_route_bfd'])
+        self.assertNotEqual(
+            router['enable_default_route_bfd'],
+            updated_router['router']['enable_default_route_bfd'])
+
+    @decorators.idempotent_id('842f6edb-e072-4805-bf11-04c25420776d')
+    def test_create_router_enable_default_route_bfd(self):
+        router1 = self._create_admin_router(data_utils.rand_name('router1'),
+                                            enable_default_route_bfd=True)
+        router2 = self._create_admin_router(data_utils.rand_name('router2'),
+                                            enable_default_route_bfd=False)
+        self.assertEqual(router1['enable_default_route_bfd'], True)
+        self.assertEqual(router2['enable_default_route_bfd'], False)
+
+    @decorators.idempotent_id('089fa304-3726-4120-9759-668e8ff1114c')
+    def test_create_router_add_external_gateways_one(self):
+        router = self._create_router(data_utils.rand_name('router'))
+        self.assertEqual(len(router['external_gateways']), 0)
+
+        res = self.client.router_add_external_gateways(
+            router['id'],
+            [{'network_id': CONF.network.public_network_id,
+              'enable_snat': False}])
+        self.assertEqual(len(res['router']['external_gateways']), 1)
+        self.assertEqual(
+            res['router']['external_gateways'][0]['network_id'],
+            CONF.network.public_network_id)
+
+    @decorators.idempotent_id('60a1e7db-04ef-4a3a-9ff1-01a990d365fd')
+    def test_create_router_add_external_gateways(self):
+        router = self._create_router(data_utils.rand_name('router'))
+        self.assertEqual(len(router['external_gateways']), 0)
+
+        res = self.client.router_add_external_gateways(
+            router['id'],
+            [
+                {'network_id': CONF.network.public_network_id,
+                 'enable_snat': False},
+                {'network_id': CONF.network.public_network_id,
+                 'enable_snat': False},
+                {'network_id': CONF.network.public_network_id,
+                 'enable_snat': False},
+            ])
+        self.assertEqual(len(res['router']['external_gateways']), 3)
+        self.assertEqual(
+            res['router']['external_gateway_info']['network_id'],
+            res['router']['external_gateways'][0]['network_id'])
+        self.assertEqual(
+            res['router']['external_gateway_info']['external_fixed_ips'],
+            res['router']['external_gateways'][0]['external_fixed_ips'])
+        for n in range(0, 3):
+            self.assertEqual(
+                res['router']['external_gateways'][n]['network_id'],
+                CONF.network.public_network_id)
+            if n:
+                self.assertNotEqual(
+                    res['router']['external_gateways'][
+                        n]['external_fixed_ips'],
+                    res['router']['external_gateways'][
+                        n - 1]['external_fixed_ips'])
+
+    @decorators.idempotent_id('e49efc57-7b25-43a3-8e55-2d87a3759c57')
+    def test_create_router_add_external_gateways_compat(self):
+        router = self._create_router(
+            data_utils.rand_name('router'),
+            external_network_id=CONF.network.public_network_id,
+            enable_snat=False)
+        self.assertEqual(len(router['external_gateways']), 1)
+        res = self.client.router_add_external_gateways(
+            router['id'],
+            [{'network_id': CONF.network.public_network_id,
+              'enable_snat': False}])
+        self.assertEqual(len(res['router']['external_gateways']), 2)
+
+    @decorators.idempotent_id('2a238eec-d9d5-435a-9013-d6e195ecd5d1')
+    def test_create_router_remove_external_gateways_compat(self):
+        router = self._create_router(
+            data_utils.rand_name('router'),
+            external_network_id=CONF.network.public_network_id,
+            enable_snat=False)
+        self.assertEqual(len(router['external_gateways']), 1)
+        res = self.client.router_remove_external_gateways(
+            router['id'],
+            [{'network_id': CONF.network.public_network_id}])
+        self.assertEqual(len(res['router']['external_gateways']), 0)
+
+    @decorators.idempotent_id('03ab196a-dac0-4363-93e4-ea799246870b')
+    def test_create_router_add_remove_external_gateways(self):
+        router = self._create_router(data_utils.rand_name('router'))
+        self.assertEqual(len(router['external_gateways']), 0)
+
+        res = self.client.router_add_external_gateways(
+            router['id'],
+            [
+                {'network_id': CONF.network.public_network_id,
+                 'enable_snat': False},
+                {'network_id': CONF.network.public_network_id,
+                 'enable_snat': False},
+                {'network_id': CONF.network.public_network_id,
+                 'enable_snat': False},
+            ])
+        self.assertEqual(len(res['router']['external_gateways']), 3)
+        remove_gateways = [res['router']['external_gateways'][2]]
+        res = self.client.router_remove_external_gateways(router['id'],
+                                                          remove_gateways)
+        self.assertEqual(len(res['router']['external_gateways']), 2)
+        for n in range(0, 2):
+            self.assertNotEqual(
+                    res['router']['external_gateways'][
+                        n]['external_fixed_ips'],
+                    remove_gateways[0])
+
+    @decorators.idempotent_id('17e94c9f-c59f-4e50-abd5-d1256460e311')
+    def test_create_router_update_external_gateways(self):
+        """Add three GW ports, delete last one, re-use IPs in update on second.
+
+        NOTE(fnordahl): Main reason for IP re-use is to ensure we don't tread
+        on allocations done by other tests.
+        """
+        router = self._create_router(data_utils.rand_name('router'))
+        self.assertEqual(len(router['external_gateways']), 0)
+
+        res = self.client.router_add_external_gateways(
+            router['id'],
+            [
+                {'network_id': CONF.network.public_network_id,
+                 'enable_snat': False},
+                {'network_id': CONF.network.public_network_id,
+                 'enable_snat': False},
+                {'network_id': CONF.network.public_network_id,
+                 'enable_snat': False},
+            ])
+        self.assertEqual(len(res['router']['external_gateways']), 3)
+        external_gateways = res['router']['external_gateways']
+        remove_gateways = [external_gateways.pop(2)]
+        res_remove_gws = self.client.router_remove_external_gateways(
+            router['id'],
+            remove_gateways)
+        for n in range(0, 2):
+            self.assertNotEqual(
+                    res_remove_gws['router']['external_gateways'][
+                        n]['external_fixed_ips'],
+                    remove_gateways[0])
+
+        external_gateways[1] = remove_gateways[0]
+        res_update_gws = self.client.router_update_external_gateways(
+            router['id'],
+            external_gateways)
+
+        self.assertEqual(len(res_update_gws['router']['external_gateways']), 2)
+        for n in range(0, 2):
+            if res_update_gws['router']['external_gateways'][
+                        n] == remove_gateways[0]:
+                break
+        else:
+            self.fail('%s not in %s' % (
+                remove_gateways[0],
+                res_update_gws['router']['external_gateways']))
+
+
 class RoutersIpV6Test(RoutersTest):
     _ip_version = 6
 
diff --git a/neutron_tempest_plugin/services/network/json/network_client.py b/neutron_tempest_plugin/services/network/json/network_client.py
index d5a827e..1153a2a 100644
--- a/neutron_tempest_plugin/services/network/json/network_client.py
+++ b/neutron_tempest_plugin/services/network/json/network_client.py
@@ -397,6 +397,9 @@
             update_body['routes'] = kwargs['routes']
         if 'enable_ndp_proxy' in kwargs:
             update_body['enable_ndp_proxy'] = kwargs['enable_ndp_proxy']
+        for attr in ('enable_default_route_bfd', 'enable_default_route_ecmp'):
+            if attr in kwargs:
+                update_body[attr] = kwargs[attr]
         update_body = dict(router=update_body)
         update_body = jsonutils.dumps(update_body)
         resp, body = self.put(uri, update_body)
@@ -471,6 +474,42 @@
     def remove_router_extra_routes(self, router_id):
         self.update_router(router_id, routes=None)
 
+    def router_add_external_gateways(self, router_id, external_gateways):
+        uri = '%s/routers/%s/add_external_gateways' % (self.uri_prefix,
+                                                       router_id)
+        update_body = {
+                'router': {'external_gateways': external_gateways},
+        }
+        update_body = jsonutils.dumps(update_body)
+        resp, body = self.put(uri, update_body)
+        self.expected_success(200, resp.status)
+        body = jsonutils.loads(body)
+        return service_client.ResponseBody(resp, body)
+
+    def router_remove_external_gateways(self, router_id, external_gateways):
+        uri = '%s/routers/%s/remove_external_gateways' % (self.uri_prefix,
+                                                          router_id)
+        update_body = {
+                'router': {'external_gateways': external_gateways},
+        }
+        update_body = jsonutils.dumps(update_body)
+        resp, body = self.put(uri, update_body)
+        self.expected_success(200, resp.status)
+        body = jsonutils.loads(body)
+        return service_client.ResponseBody(resp, body)
+
+    def router_update_external_gateways(self, router_id, external_gateways):
+        uri = '%s/routers/%s/update_external_gateways' % (self.uri_prefix,
+                                                          router_id)
+        update_body = {
+                'router': {'external_gateways': external_gateways},
+        }
+        update_body = jsonutils.dumps(update_body)
+        resp, body = self.put(uri, update_body)
+        self.expected_success(200, resp.status)
+        body = jsonutils.loads(body)
+        return service_client.ResponseBody(resp, body)
+
     def update_agent(self, agent_id, agent_info):
         """Update an agent
 
@@ -1112,6 +1151,14 @@
         self.expected_success(200, resp.status)
         return service_client.ResponseBody(resp, body)
 
+    def get_extension(self, alias):
+        uri = '%s/%s' % (
+            self.get_uri('extensions'), alias)
+        resp, body = self.get(uri)
+        self.expected_success(200, resp.status)
+        body = jsonutils.loads(body)
+        return service_client.ResponseBody(resp, body)
+
     def get_tags(self, resource_type, resource_id):
         uri = '%s/%s/%s/tags' % (
             self.uri_prefix, resource_type, resource_id)