Unlike many other monitoring tools, Nagios does not include any internal mechanisms for checking the status of hosts and services on your network. Instead, Nagios relies on external programs (called plugins) to do all the dirty work.
Documentation - Nagios Plugins
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Article ID: 361
Created On: Sun, Jan 31, 2016 at 10:36 PM
Last Updated On: Wed, Feb 10, 2016 at 7:33 PM
Authored by: tlea
Online URL: https://support.nagios.com/kb/article/nagios-core-nagios-plugins-361.html