A method for establishing a roaming connection of a communication terminal of a foreign communication network in a visited communication network, the foreign communication network and the visited communication network each comprising a plurality of sub-networks (307, 311, 315, 337, 341, 345), wherein an identification entity (309, 313, 317) for identification of a communication terminal is arranged in each sub-network (307, 311, 315) of the visited communication network, wherein a sub-network identifier (SubNW-ID1, SubNW-ID2, SubNW-IDn) is assigned to each sub-network (307, 311, 315, 337, 341, 345) of the respective communication network (303, 333), wherein in the visited communication network, a network management entity is arranged which manages assignment of sub-networks (307, 311, 315) to communication devices, the method comprising the following steps: receiving, by a first identification entity of a first sub-network of the visited communication network, a roaming connection request from the communication terminal of the foreign communication network, the roaming connection request having an identifier (UE-ID) of the communication terminal; identifying, by the first identification entity of the visited communication network, the communication terminal based on the identifier (UE-ID) of the communication terminal; requesting and receiving (403, 338) a foreign sub-network identifier (SubNW-IDx) of a foreign sub-network of the foreign communication network by the first identification entity of the visited communication network from a foreign management entity of the foreign communication network; verifying, by the network management entity or by the first identification entity, based on the foreign sub-network identifier (SubNW-IDx), whether a respective sub-network (307, 311, 315) of the visited communication network corresponds to the foreign sub-network indicated by the foreign sub-network identifier (SubNW-IDx); and sending (405, 340), by the first identification entity or the network management entity of the visited communication network, a configuration request (Cfg-Req) for a configuration of the foreign sub-network to the foreign communication network in case no respective sub-network (307, 311, 315) of the visited communication network corresponds to the foreign sub-network. receiving, by a first identification entity of a first sub-network of the visited communication network, a roaming connection request from the communication terminal of the foreign communication network, the roaming connection request having an identifier (UE-ID) of the communication terminal; identifying, by the first identification entity of the visited communication network, the communication terminal based on the identifier (UE-ID) of the communication terminal; requesting and receiving (403, 338) a foreign sub-network identifier (SubNW-IDx) of a foreign sub-network of the foreign communication network by the first identification entity of the visited communication network from a foreign management entity of the foreign communication network; verifying, by the network management entity or by the first identification entity, based on the foreign sub-network identifier (SubNW-IDx), whether a respective sub-network (307, 311, 315) of the visited communication network corresponds to the foreign sub-network indicated by the foreign sub-network identifier (SubNW-IDx); and sending (405, 340), by the first identification entity or the network management entity of the visited communication network, a configuration request (Cfg-Req) for a configuration of the foreign sub-network to the foreign communication network in case no respective sub-network (307, 311, 315) of the visited communication network corresponds to the foreign sub-network.