During an HA failover, which method updates network devices about IP-to-MAC changes?

During an HA failover, which method updates network devices about IP-to-MAC changes?

• A. Reverse ARP
• B. MAC-based forwarding
• C. Proxy ARP
• D. Gratuitous ARPs

Answer: (D)

When a high-availability failover happens, the IP address (VIP) effectively moves to a different device, so neighboring devices on the LAN may have ARP entries pointing to the old MAC. A Gratuitous ARP is an ARP announcement the new owner of the IP makes to the network, advertising the IP-to-MAC mapping without being asked. This proactive broadcast updates every device’s ARP cache so traffic is directed to the new MAC immediately, minimizing disruption and avoiding stale routes. Reverse ARP is an older mechanism used to learn IPs from a known MAC in point-to-point links, not for updating on failover. MAC-based forwarding describes how frames are forwarded using MAC addresses, not how devices learn or refresh IP-to-MAC mappings. Proxy ARP involves a router answering ARP requests on behalf of another host, which can help reachability across subnets but doesn’t in itself refresh local ARP caches after a failover. Gratuitous ARP specifically targets updating network devices about the new IP-to-MAC association in the LAN, making it the correct choice.

When a high-availability failover happens, the IP address (VIP) effectively moves to a different device, so neighboring devices on the LAN may have ARP entries pointing to the old MAC. A Gratuitous ARP is an ARP announcement the new owner of the IP makes to the network, advertising the IP-to-MAC mapping without being asked. This proactive broadcast updates every device’s ARP cache so traffic is directed to the new MAC immediately, minimizing disruption and avoiding stale routes.

Reverse ARP is an older mechanism used to learn IPs from a known MAC in point-to-point links, not for updating on failover. MAC-based forwarding describes how frames are forwarded using MAC addresses, not how devices learn or refresh IP-to-MAC mappings. Proxy ARP involves a router answering ARP requests on behalf of another host, which can help reachability across subnets but doesn’t in itself refresh local ARP caches after a failover. Gratuitous ARP specifically targets updating network devices about the new IP-to-MAC association in the LAN, making it the correct choice.