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ARP

Address Resolution Protocol

The mechanism used in IPv4 to find the address(s) that corresponds to a local IP address.

TopicIT knowledge → About 1 min read

Simple definition

ARP (Address Resolution Protocol) lets a device discover the MAC address associated with an IPv4 address on the same local network.

Technical definition

When a device needs to send an IPv4 packet to a neighbour on its local Ethernet network, it broadcasts an ARP request. The device using the requested IPv4 address replies with its MAC address; the sender caches the mapping temporarily.

What is ARP used for?

Resolve a local IPv4 address to a MAC address so an Ethernet frame can reach the correct interface.

Practical example

Before sending a packet to its default gateway at 192.168.1.1, a computer may use ARP to learn the gateway’s MAC address.

Common issues

  • Cache ARP obsolete
  • Duplicated IP Address
  • Poisoning ARP on an unprotected network

Key takeaway: This entry explains the general operation of the term. Exact settings may vary depending on software, vendors and environments.

Related resources

Relevant topic MAC Address The physical identifier of a network interface used mainly on the local network Relevant topic IP Address a logical address that identifies an interface or equipment on a network using IP protocol Relevant topic LAN Local network connecting the equipment of a home, office or site. Relevant topic Dynamic ARP Inspection Dynamic ARP Inspection is a concept or mechanism used in network & security to control responses ARP information DH...
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