Patent ID: 7151758

Claim:
A router device, comprising: at least one first interface connected with a plurality of radio base stations, each radio base station configured to accommodate at least one mobile terminal; at least one second interface connected with a network; an information exchanging unit configured to exchange a routing protocol on a network layer, through the second interface; a memory unit configured to store information regarding a routing on the network layer based on the routing protocol exchanged by the information exchanging unit; a transfer unit configured to transfer datagram through the first interface according to the information regarding the routing on the network layer stored in the memory unit; a moving detection unit configured to detect a moving of the mobile terminal among the radio base stations; and an information updating unit configured to update the information regarding the routing on the network layer stored in the memory unit when the moving of the mobile terminal is detected by the moving detection unit, wherein the transfer unit transfers the datagram through the first interface according to another information regarding a switching on a lower layer of the network layer for enabling datagram transfer along the routing on the network layer when a prescribed condition for the switching on the lower layer is satisfied.