A repeater is implemented as switches, each having ring-connection ports. In an address table in each of the switches, a list of hop numbers is stored as additional information in addition to the addresses, listing hop numbers to each of destination devices for the ring-connection ports in association with an address. When a communication controller in each of the switches finds the same destination address stored in the address table for the ring-connection ports, the communication controller selects, from the address table, one of the two destination addresses for the ring-connection ports having a smaller hop number as a transfer destination of the frame, thereby enabling the frame to take a shortest possible communication route to the destination devices.