Patent ID: 7447800

Claim:
A mobile router device, to which at least one terminal device attaches, connects a backbone network, having a plurality of access routers, to a mobile network at a first location via a first access router of the plurality of access routers, the mobile network moving within the backbone network by moving to a second location and connecting to a second access router of the plurality of access routers, the mobile router device comprising: a means for determining whether or not the mobile router device works as a master router that can connect the mobile network to the backbone network; a means for recording a virtual address common to the mobile router device attaching to the mobile network at the first location and the second location, and producing a care of address with respect to the virtual address and usable by the mobile router device at the second location; and a means for generating and transmitting a binding update message which makes the virtual address corresponding to the care of address when the mobile router device works as the master router, wherein, the mobile network further includes a backup router device, and if the backup router device determines the connection to the backbone network is lost between the mobile router device and the first access router, the backup router device transmits another binding update message that includes the virtual address corresponding to the mobile router device and another care of address corresponding to the backup router device.