Patent ID: 7339895

Claim:
A gateway device comprising: a first communication unit for connecting a first network to perform data transmission and reception to and from said first network; a second communication unit for connecting a second network to perform data transmission and reception to and from said second network with use of an IP protocol; a unit for acquiring an interface ID of a device connected to said first network and a local address of the device in said first network; a unit for acquiring a network ID of said second network; an address translation unit for generating an IPv6 address from said interface ID and network ID and managing a correspondence relation between the generated IPv6 address and said local address; and an NDP response unit for examining whether or not an IP address specified in a target address within an NS (neighbor solicitation) packet prescribed in an NDP (neighbor discovery protocol) when received from said second network is present in an IPv6 address controlled by said address translation unit, and when the IPv6 address is present, for returning an NA (neighbor advertisement) packet thereto, whereby the device connected to the first network can communicate with the device connected to said second network.