How HA chooses the active appliance

Key concepts : HA heartbeat & synchronization : How HA chooses the active appliance

An HA pair may or may not resume their active and standby roles when the failed appliance resumes responsiveness to the heartbeat.

Since the current active appliance will by definition have a greater uptime than a failed previous active appliance that has just returned online, assuming each has the same number of available ports, the current active appliance usually retains its status as the active appliance, unless Override is enabled. If Override is enabled, and if the Device Priority setting of the returning appliance is higher, it will be elected as the active appliance in the HA cluster.

If Override is disabled, HA considers (in order)

1. The most available ports

For example, if two FortiWeb appliances, FWB1 and FWB2, were configured to monitor two ports each, and FWB2 has just one port currently available according to Port Monitor, FWB1 would become the active appliance, regardless of uptime or priority. But if both had 2 available ports, this factor alone would not be able to determine which appliance should be active, and the HA cluster would proceed to the next consideration.

2. The highest uptime value

Uptime is reset to zero if an appliance fails, or the status of any monitored port (per Port Monitor) changes.

3. The smallest Device Priority number (that is, 0 has the highest priority)

4. The highest-sorting serial number


	Serial numbers are sorted by comparing each character from left to right, where 9 and z are the greatest values, and result in highest placement in the sorted list.

If Override is enabled, HA considers (in order)

1. The most available ports

2. The smallest Device Priority number (that is, 0 has the highest priority)

3. The highest uptime value

4. The highest-sorting serial number

If the heartbeat link occurs through switches or routers, and the active appliance is very busy, it might require more time to establish a heartbeat link through which it can negotiate to elect the active appliance. You can configure the amount of time that a FortiWeb appliance will wait after it boots to establish this connection before assuming that the other appliance is unresponsive, and that it should become the active appliance. For details, see the boot-time <seconds_int> setting in the FortiWeb CLI Reference.