Method for addressing an IP network connecting to another IP network

To enable a visitor network to access a host network, a method includes steps in which a router of a visitor network connects to a router of a host network and transmits to it an address request message containing an identifier of the visitor router. The host router extracts, from the address request message received, the identifier of the visitor router, and transmits, to the visitor router, an address assignment message containing either an address or an address prefix of the host network, depending on the identifier of the visitor router extracted from the address request message.