Abstract: A firewall device that executes filtering of a packet for an internal network to which a moving terminal belongs is set so that a control packet related with registration of position information about the moving terminal is allowed to pass. When the moving terminal is connected to an external network, the moving terminal transmits a control packet including position information about the self terminal to a communication terminal as communication destination. The communication terminal registers the position information included in the control packet from the moving terminal transferred from the firewall device and posts the position information to the firewall device. The firewall device updates the position information about the moving terminal based on the posted position information, and sets permission for the packet to pass between the moving terminal and the communication terminal.