The firewalls use hello message
and heartbeats to verify that the peer firewall is responsive and
operational. Hello messages are sent from one peer to the other
at the configured
Hello Interval to verify the state
of the firewall. The heartbeat is an ICMP ping to the HA peer over
the control link, and the peer responds to the ping to establish
that the firewalls are connected and responsive. By default, the
interval for the heartbeat is 1000 milliseconds. A ping is sent
every 1000 milliseconds and if there are three consecutive heartbeat
losses, a failovers occurs. For details on the HA timers that trigger
a failover, see
HA
Timers.