According to one embodiment, a communication method comprises receiving, in a first communication network for example, a packet from a terminal connected to a second communication network. The packet includes source address information therein. A determination is made whether the source address information had been changed from an original address used in the second communication network to a changed address used in the first communication address. The changed address being associated with the terminal is stored and the source address information including the changed address is provided to a terminal connected to the first communication network. Communications are supported using the source address information between the terminal connected to the first communication network and the terminal connected to the second communication network.