A level 2 (L2) switch receives a packet of upstream communication and a packet of downstream communication that are transmitted from a network device. Further, in a case where it is determined whether or not the received packet is a packet of upstream communication, and when it is determined that the packet is of session upstream communication and is a packet at a session start time, the L2 switch acquires session information and destination information included in the packet of the upstream communication, and stores in a session table. Further, when it is determined that the packet is of upstream communication and is not a packet at a session start time, and destination information of the packet is different from destination information stored in the session table, the L2 switch updates the destination information of the packet to the destination information stored in the session table.