A layer 2 switch (L2SW) includes (i) a learned information management unit for recording learned information that associates a receiving port, an address of another L2SW, and a source address specified in the original communication frame, when an encapsulated frame, in which a communication frame has been encapsulated by data containing the address of the another L2SW, is received from the backbone network and (ii) a status monitoring unit. The learned information management unit determines the update extent of the learned information, in accordance with a check result of the connection status and thus the occurrence of flooding transfer to a backbone networks side is suppressed.