SonicWall Stateful HA Upgrade NSA 3500. Software type: Upgrade

The Stateful High Availability Upgrade is offered as an optional licensed feature. Only the primary unit in the HA pair needs to be licensed. In Stateful High Availability, the primary device actively communicates with the backup device at the link and VPN levels. When the primary device creates and updates connection cache entries or VPN tunnels, the backup device is informed of the changes. The backup unit remains in a continuously synchronized state so that if the primary unit fails, it can seamlessly take over network responsibility without disrupting existing network connections.
If the Stateful High Availability Upgrade is licensed, so will the Virtual MAC capability licensed. Virtual MAC allows the backup device in an HA pair to use the MAC address of the primary device when failover occurs. Alternatively, you can manually set a virtual MAC address for both units, which will then be used. Virtual MAC addressing, like the use of virtual IP addresses, contributes to network continuity and efficiency during failover. During failover, the backup device uses the same virtual IP address that was used by the primary device. The virtual MAC feature avoids the need to update the entire network to associate the virtual IP address with the actual physical MAC address of the backup unit.