An edge switch that switches a frame between a user network and a wide area network includes an access port to connect a communication module including a storage unit storing a first identification number identifying which access port the communication module is connected to; an identification number storage unit storing a second identification number assigned to the access port; a control circuit capable of detecting a connection of the communication module; a reading unit to read the first identification number upon detection of the connection; a switchover determination unit to read the second identification number of the access port to which the connection has been detected, to compare the second and first identification numbers, and to determine that a switchover has occurred if they do not match; and a writing unit to write to the storage unit the second identification number when the switchover is determined to have occurred.