Generally, the FDB (forwarding database) 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 (Virtual Router Redundancy Protocol). 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.
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