Passive Monitoring with NRDS

Nagios Remote Data Sender, or NRDS is a component installed on a Nagios XI server that allows the administrator to create and manage configurations and plugins to be deployed with a passive agent that can be installed on a variety of operating systems.  The passive agents downloads the current configuration and the required plugin from the Nagios XI server and run the checks and posting the results to the XI server.

https://assets.nagios.com/downloads/nagiosxi/docs/Passive_Monitoring_with_NRDS.pdf