(ARP) Cache

Posted by on December 26, 2009 · Leave a Comment 

The address resolution protocol (ARP) cache is a list of recently resolved IP address to Media Access Control (MAC) address mappings. The MAC address is the unique physical address embedded in each network adapter.

If an entry in the ARP cache is incorrect, IP datagrams may be sent to the wrong computer. To display all mappings currently in the ARP cache, use the ARP command by typing arp -a at a command prompt. You should receive either a “No ARP Entries Found” message (if the ARP cache is empty) or a response similar to the following:

   Interface: 10.1.1.3 on Interface 2
   Internet Address      Physical Address      Type
   10.1.1.7              08-00-02-06-ed-20     dynamic
   10.1.1.254            08-00-02-0a-a3-10     dynamic

To remove any incorrect entries in the ARP cache, clear all entries using the following command:

arp -d <IP address>

Where <IP address> is an Internet address stored in the ARP cache. Use this command for each entry in the ARP cache until all entries have been deleted.

For more information on the syntax, options, and usage of the ARP command, type arp -? at a command prompt.

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