The relay apparatus relays frames in which a plurality of network identifiers are set and comprises a frame determining unit, a converting unit, and a sending unit. The frame determining unit determines whether a frame received at a communication port is a specific frame or not. The converting unit converts, when it is determined that the received frame is a specific frame and when the communication port is a blocking port, a network identifier set in the specific frame to another network identifier among the plurality of network identifiers. The sending unit sends the specific frame, the network identifier of which has been converted by the conversion unit, from a port opposing the communication port.