During a failover of a NetScaler HA pair, how are IP-to-MAC address bindings communicated to switches and routers on the network?

• A. The NetScaler uses Gratuitous ARPs (GARPs) to update the devices on the network.
• B. The NetScaler uses MAC-based Forwarding to update the routers.
• C. The NetScaler uses Proxy ARP to update the devices on the network.
• D. The NetScaler uses Reverse ARP (RARP) to update the devices on the network.

Answer: (A)

During failover, the network must quickly learn which NetScaler unit currently owns each VIP (IP-to-MAC mapping) so traffic is sent to the active device. The NetScaler announces these mappings by sending Gratuitous ARP messages. These are ARP packets broadcast on the network without a request, letting switches and routers refresh their ARP caches and CAM tables to point the VIPs to the new active MAC address. This enables fast convergence and prevents traffic from being sent to the old unit.

Other mechanisms don’t fit this scenario. MAC-based Forwarding isn’t a standard method used to update neighbor devices about IP-to-MAC bindings. Proxy ARP answers ARP requests on behalf of another host, which is not the mechanism used for failover updates. Reverse ARP is an older protocol that maps MAC to IP in contexts no longer common in modern networks.