Patent ID: 7965724

Claim:
A translation device for translating an Internet Protocol Version 6 (IPv6) packet having an IPv6 header into an IPv4 packet having an Internet Protocol Version 4 (IPv4) header different in header format from said IPv6 header, comprising: an IPv4 address holding unit for holding a plurality of IPv4 addresses used in an IPv4 network protocol previously; an IPv4 address assigning unit responsive to reception of said IPv6 packet, for assigning any one of said plurality of IPv4 addresses as a first IPv4 address, to a first IPv6 address used in an IPv6 network protocol and stored as a source address in the IPv6 header included in said IPv6 packet; and an address translation information exchange unit for notifying a corresponding relation between said first IPv6 address and said first IPv4 address assigned in said IPv4 address assigning unit to another translation device.