A method to establish a roaming connection of a communication terminal of a foreign communication network in a visited communication network includes receiving a roaming connection request from the communication terminal of the foreign communication network by a first identification entity of a first sub-network of the visited communication network, the roaming connection request having an identifier of the communication terminal. The method further includes identifying the communication terminal based on the identifier of the communication terminal, receiving a foreign sub-network identifier by the first identification entity of the visited communication network; verifying, on a basis of the foreign sub-network identifier, whether a respective sub-network of the visited communication network corresponds to the foreign sub-network; and sending a configuration request for a configuration of the foreign sub-network.