A communication device configured to receive a first packet from a first network including a virtual network, and to transmit a second packet to a second network, the communication device including: a receiver section configured to receive the first packet from the first network; a converter section configured to convert a second destination address of the first packet to the first destination address of the second packet using identifying information of the virtual network; a selector configured to select a security parameter based at least in part on the first destination address of the second packet; an encryption section configured to encrypt the second packet based on the security parameter; and a transmitter section configured to multicast the encrypted second packet to the second network.