• ARP is a protocol used by the Internet Protocol(IP) to map the logical address(IP address) to its physical address(Mac address).
• The logical address(IP) is obtained from the DNS if the sender is a host or its obtained from routing table if sender happens to be a router.
• But the IP datagram must be encapsulated in a frame to be able to pass through physical network. This means sender must know the physical address.
• The sender sends a ARP query which consist of its physical address and IP address.
• This ARP query is a broadcast over the network and it is received by all the deviies in the network.
• This ARP request is dropped by all the recipient except for the one for which it is meant to be.
• The correct recipient processes the ARP Query and updates its MAC table with the sender IP and sender Mac address and sends a unicast message to the sender with its physical address.
• Upon receiving the ARP reply , sender updates its MAC table with the received mac address.i
• Since the physical address is known now, it does not need to do the ARP query henceforth for the same recipient. This is called ARP caching.

ARP REQUEST AND REPLY:

ARP ENCAPSULATION:

Categories: Networking