A failover group is simply a logical group of one or more security contexts. In Active/Active failover, you divide the security contexts on the ASA into 2 failover groups. Active/Active failover is only available to ASAs in multiple context mode. In an Active/Active failover configuration, both ASAs can pass network traffic.You can use Active/Standby failover for ASAs in single or multiple context mode.

When a failover occurs, the active unit fails over to the standby unit, which then becomes active.

The standby unit does not actively pass traffic.

In Active/Standby failover, one unit is the active unit.

Each failover configuration has its own method for determining and performing failover. The ASA supports two failover configurations, Active/Active failover and Active/Standby failover. If those conditions are met, failover occurs. The health of the active interfaces and units is monitored to determine if specific failover conditions are met. Configuring high availability requires two identical ASAs connected to each other through a dedicated failover link and, optionally, a Stateful Failover link.

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