Address Resolution Protocol (ARP) is a protocol used to map IP addresses to MAC addresses.
ARP is required to map IP addresses to MAC addresses.
For hosts or other Layer 3 network devices to communicate on a LAN, the sender must know the destination IP address to which it will send IP packets. The IP packets, however, must first be encapsulated with MAC addresses before they can be transmitted over the physical network. It is therefore necessary for hosts or Layer 3 network devices to maintain an ARP table for storing the mapping information of IP and MAC addresses. There are generally two types of ARP entries: static and dynamic.