Patent ID: 8861385

Claim:
A communication device comprising: an address selection unit which selects a layer 2 address that is a change candidate for the communication device; a presence check request generation unit which generates a presence check request message, the presence check request message storing, in a destination layer 2 address storage area, only the layer 2 address selected by the address selection unit, the presence check request message storing, in a transmission source layer 2 address storage area, a current layer 2 address of the communication device, the presence check request message storing, in a destination layer 3 address storage area, at least one of a broadcast address and a multicast address; a presence check request transmission unit which transmits the presence check request message generated by the presence check request generation unit via a network to which the communication device is connected; a presence check response receiving unit which receives a presence check response message to the presence check request message via the network to which the communication device is connected; an address duplication determination unit which determines that a communication device having the layer 2 address selected by the address selection unit is present on the network when it is discriminated that there is the presence check response message received by the presence check response receiving unit, and determines that the communication device having the layer 2 address selected by the address selection unit is not present on the network when it is discriminated that there is no presence check response message received by the presence check response receiving unit; and an address change unit which changes a current layer 2 address for a communication interface of the communication device into the layer 2 address selected by the address selection unit when a communication device having the layer 2 address selected by the address selection unit is found not to be present on the network based on the determination of the address duplication determination unit.