The devices in an HA pair can be assigned a device
priority value to indicate a preference for which device
should assume the active role and manage traffic upon failover.
If you need to use a specific device in the HA pair for actively
securing traffic, you must enable the preemptive behavior on both
the firewalls and assign a device priority value for each device.
The device with the lower numerical value, and therefore higher
priority, is designated as active and manages all traffic
on the network. The other device is in a passive state, and synchronizes
configuration and state information with the active device so that
it is ready to transition to an active state should a failure occur.
By default, preemption is disabled on the firewalls and must
be enabled on both devices. When enabled, the preemptive behavior
allows the firewall with the higher priority (lower
numerical value) to resume as active after it recovers from a failure.
When preemption occurs, the event is logged in the system logs.