Address Resolution Protocol(ARP)

  • 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.


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Categories: Networking

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