Choosing Active or Passive Montioring with Nagios

When setting up alerts in Nagios some are better to be active while others can be passive.  Further Active monitoring can be executed either on the Nagios server or started from Nagios but executed remotely, see diagram.

1. Active Service Checks are initated by Nagios
   • Ping or service check of exposed resources
   • Remote Execution (nrpe) (ssh) for checking local resources like disk usage, processor load
2. Passive Service Checks are initated by exteral commands
   • Passive Checks are good for handling asynchronous events such as:
     • security alerts
     • when scanning log files for errors
     • handling alerts from 3rd party software.