Benefits

Stateful Hardware Failover provides the following benefits:

Improved reliability

• By synchronising most critical network connection information, Stateful Hardware Failover prevents down time and dropped connections in case of appliance failure.

Faster failover performance

• By maintaining continuous synchronisation between the primary and backup appliances, Stateful Hardware Failover enables the backup appliance to take over in case of a failure with virtually no down time or loss of network connections.

Minimal impact on CPU performance

• Typically less than 1% usage.

Minimal impact on bandwidth

• Transmission of synchronisation data is throttled so as not interfere with other data.

How Does Stateful Hardware Failover Work?

Stateful Hardware Failover is not load-balancing. It is an active-passive configuration where the primary appliance handles all traffic. When Stateful Hardware Failover is enabled, the primary appliance actively communicates with the backup to update most network connection information. As the primary appliance creates and updates network connection information (VPN tunnels, active users, connection cache entries, etc.), it immediately informs the backup appliance. This ensures that the backup appliance is always ready to transition to the active state without dropping any connections.

The synchronisation traffic is throttled to ensure that it does not interfere with regular network traffic. All configuration changes are performed on the primary appliance and automatically propagated to the backup appliance. The hardware failover pair uses the same LAN and WAN IP addresses—regardless of which appliance is currently active. When using SonicWALL Global Management System (GMS) to manage the appliances, GMS logs into the shared WAN IP address. In case of a failover, GMS administration continues seamlessly, and GMS administrators currently logged into the appliance will not be logged out, however Get and Post commands may result in a timeout with no reply returned.