Use the following procedure to configure Gratuitous Address Resolution Protocol (ARP). When Gratuitous ARP is enabled the switch allows all Gratuitous ARP request packets. The default is enabled.
If you disable Gratuitous ARP, the switch only allows Gratuitous ARP packets associated with Routed Split Multi-Link Trunking (RSMLT) or Virtual Router Redundancy Protocol (VRRP), and the switch discards all other Gratuitous ARP request packets.
ARP translates network layer (layer 3) IP addresses into link layer (layer 2) MAC addresses. A host sends a Gratuitous ARP request packet to inform other hosts of the existence of an interface on the network, so other local hosts can update their ARP tables. If the IP or MAC address changes, or in the event of a failover, a host sends a Gratuitous ARP request packet to inform other hosts to update their ARP tables.
VRRP and RSMLT use gratuitous ARP to update the MAC address tables on switches.