Disclosed is a technique which enables a communication node connected to a router made to advertise a plurality of prefixes to use an address including an appropriate prefix. According to this technique, an MR (Mobile Router) (10) multicasts, to a mobile PAN (31), a router advertisement message including a prefix (MNPNEMO) derived from a home network to which it pertains, a prefix (MNPAR) advertised from an AR (access router) (10a) and prefix choice information indicative of one of the prefixes to be selected on the basis of a function relative to the mobile PAN (31). A node (VN 20a, LN 20b) connected to the mobile PAN refers to the prefix choice information of the router advertisement message so as to select a prefix appropriate thereto for configuring its own global address.