Obtaining nagios and Nagios plugins

The latest release of Nagios plugins can find out at -

https://www.nagios.org/downloads/nagios-plugins/

Also on,

https://www.nagios.org/projects/nagios-plugins/

Nagios core can be downloaded for free from below link -

https://www.nagios.org/downloads/

All previous releases are available on the official Nagios website.