The SonicWall Stateful High Availability Upgrade is an essential licensed feature that ensures your network remains operational even during primary unit failures. This upgrade allows the primary unit to communicate actively with its backup counterpart, maintaining synchronization of connection caches and VPN tunnels. In the event of a primary unit failure, the backup unit can take over instantly, ensuring no disruption to existing network connections. Additionally, this upgrade includes Virtual MAC capability, which allows the backup unit to adopt the MAC address of the primary unit during failover, enhancing network continuity and efficiency. This feature eliminates the need for network-wide updates to associate the virtual IP address with the backup unit's physical MAC address, streamlining the failover process and maintaining service integrity.