Packet switch for interfacing between LAN and WAN

A packet switch interfacing between a WAN and a LAN accommodating a terminal includes an address table storing a relation between an address of the terminal and an input port receiving a packet transmitted from the terminal, and an address learning unit for storing in the address table the relation between the source address of the received packet and the input port receiving the received packet. Further the packet switch includes a SW unit for effecting control to transmit the received packet according to whether or not stored in the address table, and then transmit the received packet to the WAN when a packet having a source address identical with the destination address of the received packet has not been received from the LAN.