Critical Active Monitors

Critical active monitors pair the features of critical monitor precedence with an active monitor or script you apply to assess or indicate device health. Monitor precedence is useful for high traffic periods where the device being monitored is functioning but the path to the device causes delays in poll or ping response which could indicate down status. For example, for devices running critical services, you can apply a critical active monitors to open a basic Telnet connection, a remote login session, survey the mission critical device or service through a dedicated management segment and interface (and so on).

It is best practice to escalate monitors relative to the service or application you want to ensure continuity for. So, if you are monitoring for availability of a critical web service, you could make an HTTP monitor dependent on the Ping monitor —where the HTTP monitor would be critical.

Polling Precedence

In a critical monitor polling path, critical monitors are polled first. If you specify more than one critical monitor, you also specify the order in which they are polled. Critical monitors are "up" dependent on one another; if critical monitors return successful results, non-critical monitors are polled. If any of the critical monitors go down, all active monitors behind it in the critical polling order are no longer polled and are placed in an unknown state for the duration of the polling cycle. In addition performance monitors are no longer polled and are placed in an unknown state for the duration of the polling cycle.

The following table describes the exception to this rule:

IF	AND	THEN
The first critical monitor goes down	The critical monitors behind it in the critical polling order are APM Active or Performance monitors	All other critical monitors will continue to poll.
The first critical monitor goes down	The critical monitors behind it in the critical polling order are Wireless monitors	All other critical monitors will continue to poll.
The first critical monitor goes down	The critical monitors behind it in the critical polling order are Active script monitors	All other critical monitors will continue to poll.
The first critical monitor goes down	The critical monitors behind it in the critical polling order are Active script performance monitors	All other critical monitors will discontinue to poll.

If at the start of the next polling cycle, the critical monitor returns successful results, polling of successive critical monitors and non-critical monitors resumes.

Note: Up and Down device dependencies take precedence over critical monitor polling; if WhatsUp Gold detects device dependencies, the configured dependencies are respected.

When critical monitoring is enabled, and you specify a critical polling order, you now receive only one alert when a device loses its network connectivity.

Note: When a monitor is placed in the unknown state, assigned actions are not fired. Likewise, when a monitor comes out of the unknown state into an Up state, assigned actions are not fired.

Only monitors that you specify as critical follow a specific polling order; non-critical monitors are not polled in any specific order. Additionally, if multiple non-critical monitors fail, all associated actions fire.

Note: Independent poll frequency for all monitors is ignored when a monitor is specified as critical.