Method for addressing an IP network connecting to another IP network

Access procedure a visitor network (2) to a core network (1), comprising steps during which a router (12) of the visitor network connects (21) to a router (10) of the network main and transmits (24) a request message address, wherein the message address request contains an identifier of the visitor router (12), the method further comprising steps during which the host router (10) extracts message address request received the identifier of the visitor router and transmits (27, 28) in reply to the visitor a message attributing address containing either an address or a prefix address of the main network router (1 ), depending on the visitor router identifier extracted from the address request message.