Possible Failover Event Situations
Failure Condition Reasons That Standby Becomes Active
No Failure Failover active—An administrator can force the standby unit
to change state by using the failover active command, which
causes failover to occur. This is the only situation in which
failover occurs without the primary (active) unit having any
problems. A no failover active command will return the
active unit back to the standby unit.
Power loss or reload Cable errors—The cable is wired so that each unit can
distinguish between a power failure in the other unit and an
unplugged cable. If the standby unit detects that the active
unit is turned off (or resets), it takes active control.
Loss of power—When the primary (active) unit loses power
or is turned off, the standby unit assumes the active role.
PIX Firewall hardware failure Memory exhaustion—If block memory exhaustion occurs
for 15 straight seconds on the active unit the standby unit
becomes the active unit.
Network failure Failover communication loss—If the standby unit does not
hear from the active unit for more than twice the configured
poll time (or a maximum of 30 seconds), and the cable status
is OK, a series of tests is conducted before the standby unit
takes over as active.