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Gratuitios ARP.

chandra_rc16
Enthusiast
Enthusiast

Will each and every PC generate gratuitous ARP when added a LAN Segment.

Can somone please explain about thigs ?    

Regards,

Chandu

Regards, Chandu
2 Replies 2

Reza Sharifi
Hall of Fame
Hall of Fame

Have a look at this under the the Gratuitous ARP section.

http://cauew.blogspot.com/2008/08/arp-rarp-proxy-arp-gratuitous-arp-and.html

HTH

Jon Marshall
Hall of Fame
Hall of Fame

Chandu

No they won't. When a PC is added to a LAN segment there is no need for a gartuitous arp. The PC will use arp to resolve -

1) the mac address of any other device in the same vlan

2) the mac address of the PCs default gateway

A gratuitous arp is generally used when a device needs to update other devices that the mac address to IP mapping has changed. Because arp entries are kept in a cache they take a certain amount of time before they are removed or renewed. If during that time a device in the arp cache changes it's mac address the PC would not be able to communicate with it because it would still be using the old mac address. A gratuitous arp solves this problem.

You often see gratuitous arps being used in failover situations where the stanbdy device becomes active and because the standby device is using a different mac address it needs to tell all end devices of the new mac to IP address mapping.

Jon

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