Patent ID: 7979582

Claim:
A communication device that manages network layer addresses and data link layer addresses in association with each other, said communication device comprising: a processor; an Address Resolution Protocol (ARP) receiving unit operable to receive ARP packets transmitted by ARP; a duplication detecting unit operable to detect, using said processor, a Gratuitous ARP (GARP) packet in which a network layer address of a transmitting source matches a network layer address of said communication device, from among the ARP packets received by said ARP receiving unit; a duplication notification generating unit operable to generate an ARP reply packet notifying the transmitting source that the network layer address is duplicated, when the GARP packet is detected by said duplication detecting unit; an update GARP generating unit operable to generate an update GARP packet in which the network layer address and the data link layer address of said communication device are set up, when the GARP packet is detected by said duplication detecting unit; and an ARP transmitting unit operable to transmit, by ARP, the ARP reply packet generated by said duplication notification generating unit, and to transmit, by GARP, the update GARP packet generated by said update GARP generating unit.