To simulate an existing LAN communication at a high speed efficiently based on the 'LAN emulation-over ATM specifications' specified by the ATM forum in the case of using existing protocols such as TCP/IP in an ATM exchange network.

An LECa makes an IP/MAC-ARP request to a BUS to obtain a MAC address from an opposite IP address (β), the BUS searches whether or not the IP address (β) is in existence in an ARP search table, and returns a MAC address (Y) on the ARP cache table to the LECa when the corresponding address is in existence. If the corresponding IP address is not registered in the ARP search table, the IP/MAC-ARP request is transferred to all LECs by a multi-cast VCC.