Address Resolution Protocol In TCP/IP, a protocol that uses broadcast traffic on the local network to resolve a logically assigned Internet Protocol version 4 (IPv4) address to its physical hardware or media access control (MAC layer address). In asynchronous transfer mode (ATM), ARP is used two different ways. For classical IPv4 over ATM (CLIP), ARP is used to resolve addresses to ATM hardware addreses. For ATM LAN emulation (LANE), ARP is used to resolve Ethernet/802.3 or Token Ring addresses to ATM hardware addresses