During HA failover, which mechanism does the Citrix ADC use to inform network devices about updated IP-to-MAC bindings?

During HA failover, which mechanism does the Citrix ADC use to inform network devices about updated IP-to-MAC bindings?

• A. Reverse ARP (RARP).
• B. MAC-based forwarding (MBF).
• C. Proxy ARP.
• D. Gratuitous ARPs (GARPs).

Answer: (D)

When a failover happens, the active Citrix ADC that hosts the VIP may change, so the IP-to-MAC binding seen by devices on the LAN must be refreshed. Gratuitous ARP is the mechanism used to broadcast an unsolicited ARP message for the relevant IP, announcing the new MAC address associated with that IP. This prompts switches and hosts on the network to update their ARP caches, ensuring subsequent traffic is directed to the new active unit without waiting for a normal ARP request/response cycle. This approach also helps quickly detect any IP conflicts, since devices will respond or flag duplicates when they see the unexpected ARP announcements. Other options serve different purposes: Reverse ARP is an old method for devices to learn their own IP from a MAC and isn’t used to inform others about binding changes; MAC-based forwarding is a forwarding optimization, not a mechanism for updating ARP tables; Proxy ARP answers ARP requests on behalf of another device and isn’t the standard method for conveying a new binding during failover. Gratuitous ARP is specifically designed to advertise the new IP-to-MAC binding after failover.

When a failover happens, the active Citrix ADC that hosts the VIP may change, so the IP-to-MAC binding seen by devices on the LAN must be refreshed. Gratuitous ARP is the mechanism used to broadcast an unsolicited ARP message for the relevant IP, announcing the new MAC address associated with that IP. This prompts switches and hosts on the network to update their ARP caches, ensuring subsequent traffic is directed to the new active unit without waiting for a normal ARP request/response cycle.

This approach also helps quickly detect any IP conflicts, since devices will respond or flag duplicates when they see the unexpected ARP announcements. Other options serve different purposes: Reverse ARP is an old method for devices to learn their own IP from a MAC and isn’t used to inform others about binding changes; MAC-based forwarding is a forwarding optimization, not a mechanism for updating ARP tables; Proxy ARP answers ARP requests on behalf of another device and isn’t the standard method for conveying a new binding during failover. Gratuitous ARP is specifically designed to advertise the new IP-to-MAC binding after failover.