PACKET TRANSFER APPARATUS PERFORMING ADDRESS TRANSLATION

A packet transfer apparatus having a plurality of protocol processing units 10 and a switch 20 for switching IP packets among the protocol processing units, wherein a protocol processing unit connected to an IPv4 network includes: input-side address translator CNv6 (I) for translating the address of an input packet to an IPv6 address; output-side address translator CNv4 (O) for translating, when an IPv6 packet is received from the switch, the address to an IPv4 address and transferring the resultant packet to the IPv4 network; and an operation mode controller for omitting address translation by the input-side address translator.