What is a Passive check in Nagios?

In Nagios, we can monitor hosts and services by active checks. In addition, Nagios also supports Passive checks that are initiated by external applications.

The results ofPassivechecksaresubmitted to Nagios. There are two main use cases of passive checks:

1. We use Passivechecks to monitor synchronous services that do not give positive results with Activechecksat regular intervals of time.
2. We can use Passivechecks to monitor services or applications that are located behind a firewall.