High Availability Modes

High Availability has several operation modes, which can be selected on the High Availability > Settings page:

•
None—Selecting None activates a standard high availability configuration and hardware failover functionality, with the option of enabling Stateful HA and Active/Active DPI.
•
Active/Standby—Active/Standby mode provides basic high availability with the configuration of two identical firewalls as a High Availability Pair. The Active unit handles all traffic, while the Standby unit shares its configuration settings and can take over at any time to provide continuous network connectivity if the Active unit stops working.

By default, Active/Standby mode is stateless, meaning that network connections and VPN tunnels must be re-established after a failover. To avoid this, Stateful Synchronization can be licensed and enabled with Active/Standby mode. In this Stateful HA mode, the dynamic state is continuously synchronized between the Active and Standby units. When the Active unit encounters a fault condition, stateful failover occurs as the Standby firewall takes over the Active role with no interruptions to the existing network connections.

•
Active/Active DPI—The Active/Active Deep Packet Inspection (DPI) mode can be used along with the Active/Standby mode. When Active/Active DPI mode is enabled, the processor-intensive DPI services, such as Intrusion Prevention (IPS), Gateway Anti-Virus (GAV), and Anti-Spyware, are processed on the standby firewall, while other services, such as firewall, NAT, and other types of traffic, are processed on the Active firewall concurrently.
* 
NOTE: Active/Active DPI is not supported on the NSA 3600, or NSA 4600.
•
Active/Active Clustering—In this mode, multiple firewalls are grouped together as cluster nodes, with multiple Active units processing traffic (as multiple gateways), doing DPI and sharing the network load. Each cluster node consists of two units acting as a Stateful HA pair.

Active/Active Clustering provides Stateful Failover support in addition to load-sharing. Optionally, each cluster node can also consist of a single unit, in which case Stateful Failover and Active/Active DPI are not available.

* 
NOTE: Active/Active Clustering is supported by default on the SM 9000 series. Active/Active Clustering is supported on NSA 5600 and NSA 6600 only with the purchase of a SonicOS Expanded License. Licenses can be purchased at www.MySonicWall.com.
•
Active/Active DPI Clustering—This mode allows for the configuration of up to four HA cluster nodes for failover and load sharing, where the nodes load balance the application of DPI security services to network traffic. This mode can be enabled for additional performance gain, utilizing the standby units in each cluster node.