Virtual MAC Address

The Virtual MAC address allows the High Availability pair to share the same MAC address, which reduces convergence time following a failover. Convergence time is the amount of time it takes for the devices in a network to adapt their routing tables to the changes introduced by high availability.

Without Virtual MAC enabled, the Active and Standby firewalls each use their own MAC addresses. Because the firewalls are using the same IP address, when a failover occurs, it breaks the mapping between the IP address and MAC address in the ARP cache of all clients and network resources. The Standby firewall must send a gratuitous ARP message that announces the new MAC address and IP address pair. Until this ARP request propagates through the network, traffic intended for the Active firewall’s MAC address can be lost.

The Virtual MAC address greatly simplifies this process by using the same MAC address for both the Active and Standby firewalls. When a failover occurs, all routes to and from the Active firewall are still valid for the Standby firewall. All clients and remote sites continue to use the same Virtual MAC address and IP address without interruption.

By default, this Virtual MAC address is provided by the SonicWall firmware and is different from the physical MAC address of either the Primary or Secondary firewalls. This reduces configuration errors and ensures the uniqueness of the Virtual MAC address, which prevents possible conflicts. Optionally, you can manually configure the Virtual MAC address on DEVICE | High Availability > Monitoring.

The Virtual MAC setting is available even if Stateful High Availability is not licensed. When Virtual MAC is enabled, it is always used even if Stateful Synchronization is not enabled.