Adding Virtual MAC Entries from IP ARP Packets

Generally, the FDB is programmed with the source MAC address of frames that contain an IP ARP payload. MAC entries present in the ARP payload as Sender-MAC are not learned. When IP ARP Sender-MAC learning is enabled, the switch learns both the source MAC address and the Sender-MAC from the ARP payload, and the switch programs these MAC addresses in the FDB.

This feature is useful when you want the switch to learn the Sender-MAC address for a redundant protocol, such as VRRP. For example, if your network has a gateway with a virtual MAC address, the switch learns the system MAC address for the gateway. If you enable the IP ARP Sender-MAC learning feature, the switch also learns the virtual MAC address embedded in IP ARP packets for the gateway IP address.