def test__set_subnet_arp_info(self):
        agent = l3_agent.L3NATAgent(HOSTNAME, self.conf)
        router = l3_test_common.prepare_router_data(num_internal_ports=2)
        router['distributed'] = True
        ri = dvr_router.DvrLocalRouter(
            agent, HOSTNAME, router['id'], router, **self.ri_kwargs)
        ports = ri.router.get(l3_constants.INTERFACE_KEY, [])
        subnet_id = l3_test_common.get_subnet_id(ports[0])
        test_ports = [{'mac_address': '00:11:22:33:44:55',
                      'device_owner': 'network:dhcp',
                      'fixed_ips': [{'ip_address': '1.2.3.4',
                                     'prefixlen': 24,
                                     'subnet_id': subnet_id}]}]

        self.plugin_api.get_ports_by_subnet.return_value = test_ports

        # Test basic case
        ports[0]['subnets'] = [{'id': subnet_id,
                                'cidr': '1.2.3.0/24'}]
        ri._set_subnet_arp_info(subnet_id)
        self.mock_ip_dev.neigh.add.assert_called_once_with(
            '1.2.3.4', '00:11:22:33:44:55')

        # Test negative case
        router['distributed'] = False
        ri._set_subnet_arp_info(subnet_id)
        self.mock_ip_dev.neigh.add.never_called()