Gratuitous ARP

Gratuitous ARP, or GARP, refers to an unsolicited ARP message within an IPv4 network. A device announces the mapping between its own IP address and corresponding MAC address without receiving a previous ARP request. Other network devices can use this information to update their ARP tables. Gratuitous ARP is commonly used following MAC address changes, for detecting duplicate IP addresses and in high-availability environments. After a failover, for example, a newly active system can announce its MAC address for an existing IP address. This enables network traffic to be redirected to the new destination more quickly. GARP therefore supports address information updates and rapid failover processes within local networks.