A network system including a mobile node, a correspondent node for transmitting/receiving a data packet to/from the mobile node, a first router to which the mobile node is connected at a visited domain and a second router to which the mobile node is connected at a moving destination to which the mobile node moves from the first router. The second router including a location registration message generating unit for generating a location registration message of the mobile node and transmitting the location registration message. The first router including a binding cache, a movement managing unit for receiving the location registration message and storing into the binding cache address information from before and after the mobile node moves and an encapsulating unit for receiving the data packet, encapsulating the data packet concerned, and creating and transmitting a data packet containing as a transmission destination the address information after the change.