code: def _attach_dummy_intf_rtr(self, tenant_id, tenant_name, rtr_id):
          
          serv_obj = self.get_service_obj(tenant_id)
          fw_dict = serv_obj.get_fw_dict()
          fw_id = fw_dict.get('fw_id')
          rtr_nwk = fw_id[0:4] + fw_const.DUMMY_SERVICE_NWK + (
              fw_id[len(fw_id) - 4:])
          net_id, subnet_id = self.os_helper.create_network(
              rtr_nwk, tenant_id, self.servicedummy_ip_subnet)
          if net_id is None or subnet_id is None:
              return None, None
          net_dict = {}
          net_dict['name'] = rtr_nwk
          self.store_net_db(tenant_id, net_id, net_dict, 'SUCCESS')
          subnet_lst = set()
          subnet_lst.add(subnet_id)
          if rtr_id is None:
              self.os_helper.delete_network(rtr_nwk, tenant_id, subnet_id,
                                            net_id)
              return None, None
          ret = self.os_helper.add_intf_router(rtr_id, tenant_id, subnet_lst)
          if not ret:
              self.os_helper.delete_network(rtr_nwk, tenant_id, subnet_id,
                                            net_id)
              return None, None
          return net_id, subnet_id
docs: Function to create a dummy router and interface.