A mobile communication method comprising: transmitting, by a mobile router to a home agent, a binding update message in which the mobile router, managing a mobile local network moving between networks as one unit, notifies the home agent of a care-of-address of the mobile router which was acquired at a network to which the mobile local network has gone; determining, by the mobile router based on information received from the home agent in a binding acknowledgment message, whether the home agent, at a time the home agent receives the binding update message, has without delay sent routing information concerning a route to the mobile local network which the mobile router manages to a gateway of a home network, the routing information comprising an instruction to transfer data addressed to the mobile local network to the home agent; responsive to the home agent having sent the routing information to the gateway of the home network, the gateway updates its routing table based on the routing information; and responsive to the mobile router determining that the home agent has not sent the routing information to the gateway of the home network, sending, by the mobile router to the home agent, a further message using a routing protocol to indicate the routing information to the home agent, and notifying, by the home agent, the routing information to the home network, wherein: the determining of whether the home agent has without delay sent the routing information to the gateway of the home network includes determining whether the received binding acknowledgment message includes an acknowledgment flag that indicates that the home agent has sent the routing information to the gateway, and responsive to the received acknowledgment flag indicating that the home agent has not sent the routing information to the gateway, the sending, by the mobile router to the home agent, of the routing information, as the further message, is done via a tunnel to the mobile local network, and the tunnel is established between the mobile router and the home agent. transmitting, by a mobile router to a home agent, a binding update message in which the mobile router, managing a mobile local network moving between networks as one unit, notifies the home agent of a care-of-address of the mobile router which was acquired at a network to which the mobile local network has gone; determining, by the mobile router based on information received from the home agent in a binding acknowledgment message, whether the home agent, at a time the home agent receives the binding update message, has without delay sent routing information concerning a route to the mobile local network which the mobile router manages to a gateway of a home network, the routing information comprising an instruction to transfer data addressed to the mobile local network to the home agent; responsive to the home agent having sent the routing information to the gateway of the home network, the gateway updates its routing table based on the routing information; and responsive to the mobile router determining that the home agent has not sent the routing information to the gateway of the home network, sending, by the mobile router to the home agent, a further message using a routing protocol to indicate the routing information to the home agent, and notifying, by the home agent, the routing information to the home network, wherein: the determining of whether the home agent has without delay sent the routing information to the gateway of the home network includes determining whether the received binding acknowledgment message includes an acknowledgment flag that indicates that the home agent has sent the routing information to the gateway, and responsive to the received acknowledgment flag indicating that the home agent has not sent the routing information to the gateway, the sending, by the mobile router to the home agent, of the routing information, as the further message, is done via a tunnel to the mobile local network, and the tunnel is established between the mobile router and the home agent.