#status/done

Address Resolution Protocol

The Address Resolution Protocol (ARP) is designed to associate Network Layer addresses to Link Layer addresses. In this case, we're concerned with IP addresses and MAC addresses. This allows switches to transmit ethernet frames to their intended destination devices on the Local Area Network (LAN).

Machine A begins the protocol by broadcasting a frame containing three pieces of data:

  1. The source, which is the machine's own MAC address.
  2. The destination, ff:ff:ff:ff:ff:ff as the destination. This is a special address meaning broadcast and allows every machine on the network to receive the frame.
  3. A string, which when roughly translated into English is equivalent to asking: "Who has the IP address belonging to Machine B? Please tell Machine A."

Machine A sends this frame and then Machine B receives it. Because of the information included in the broadcasted frame, Machine B now knows the MAC address of Machine A. Machine B then responds with its own frame, which also contains three pieces of data:

  1. Its MAC address as the source.
  2. Machine A's MAC address as the destination.
  3. A string, which again roughly translated into English says: "My IP address is at this MAC address."

Relevant Note(s): Network Protocols