The firewalls use hello message and heartbeats to verify
that the peer device 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 device. 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 devices are connected
and responsive. For details on the HA timers that trigger a failover,
see HA Timers.
(The HA timers for the VM-Series firewall are the same as that of
the PA-5000 Series firewalls).