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 of Passive checks are submitted to Nagios. There are two main use cases of Passive checks:
- We use Passive checks to monitor asynchronous services that do not give positive result with Active checks at regular intervals of time.
- We can use Passive checks to monitor services or applications that are located behind a firewall.