During a Citrix ADC high availability (HA) failover, the secondary appliance takes over the primary role and all associated IP addresses (e.g., VIPs, SNIPs). To ensure traffic is immediately redirected to the new primary appliance, it must update the ARP caches of adjacent network devices (switches and routers). The new primary appliance accomplishes this by broadcasting Gratuitous ARP (GARP) packets for each IP address it now owns. These unsolicited ARP messages announce the new IP-to-MAC address binding, compelling network devices to update their tables and forward subsequent traffic to the correct physical port.

A. Reverse ARP (RARP) to update the network devices:

RARP is an obsolete protocol used by a client machine to request its own IPv4 address from a network, given its MAC address. It does not announce IP-to-MAC mappings to other devices.

B. MAC-based forwarding (MBF) to update the routers:

MAC-based forwarding (MBF) is a Layer 2 forwarding mode on the Citrix ADC itself. It is not a protocol used to communicate state changes or update external network devices during an HA failover.

C. Proxy ARP to update the network devices:

Proxy ARP is a technique where a device responds to ARP requests on behalf of another device. It is not the mechanism used to proactively broadcast an updated IP-to-MAC mapping after a failover event.

1. Citrix Product Documentation - High Availability: "When a failover occurs

the new primary node sends gratuitous ARP (GARP) packets to announce that it is now the owner of the Citrix ADC owned IP addresses. The network devices then update their ARP tables."

Source: Citrix ADC 13.1 Product Documentation

"High availability

" Section: "Failover."

2. Citrix Product Documentation - Configuring High Availability Nodes: "After a failover

the new primary sends a set of gratuitous ARP (GARP) messages to notify the network of the change. The GARP messages are broadcast to the network."

Source: Citrix ADC 13.1 Product Documentation

"High availability deployment

" Section: "Configuring high availability nodes."

3. Citrix Product Documentation - Troubleshooting High Availability: "The new primary broadcasts gratuitous ARP (GARP) packets to update the ARP tables of the neighboring routers."

Source: Citrix ADC 13.1 Product Documentation

"Troubleshooting

" Section: "Troubleshooting High Availability."