ARP (Address Resolution Protocol ) | Tech Info Home Page |

General Information

Address Resolution Protocol (ARP)

A networking protocol which is responsible for determining the MAC address of a frame by performing a resolution of IP addresses to MAC addresses on outgoing packets. This information is used by the Network access Layer of the OSI model. The MAC address is 48 bits and the IP address is 32 bits long.

ARP allows the requesting computer to find the MAC address of another computer on the same physical network using the destination computer's IP address.

Typically the ARP sequence is as follows.

1) The Network Layer accepts an IP packet. The local cache is searched for a match between the destination IP address and the MAC address and if one is found the packet is forwarded to that address.

2) When the cache does not have an entry for the requested address, an ARP request is broadcasted to all computers on the network. If any receiving host has a matching address, it responds to the ARP request with its MAC address.

3) The originating computer adds the address to its table and sends the packet to the proper destination.

ARP is controlled by the RFC 826 standard.

Microsoft Implementation 

• See the NT 4.0 ARP page

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