Nagios software details

Nagios has three major software components

1. Nagios Core : This needs to be installed on Nagios collector. It includes nagios executable responsible for data collection and processing.
   
2. Nagios Agent: This needs to be installed on monitored systems (hosts). It responds to the collector's query by executing specified plugin on the host. Windows agent is named as NSClient++, Linux/Unix agent is named as NRPE.
   
3. Nagios Plugins:  This software needs to be installed on the collector and monitored Linux/Unix hosts. There is no need of separate plugins installation for Windows system as they are packaged with Nagios agent. 

Nagios Software Download links

1. Nagios Core source: 

http://prdownloads.sourceforge.net/sourceforge/nagios/nagios-3.4.1.tar.gz

2. Nagios Agent binaries for Windows:

NSClient++(64bit) http://files.nsclient.org/x-0.3.x_STABLE/NSClient%2B%2B-0.3.9-x64.zip

NSClient++(32bit) http://files.nsclient.org/x-0.3.x_STABLE/NSClient%2B%2B-0.3.9-Win32.zip

3. Nagios Agent source for Linux:

(NRPE)  http://prdownloads.sourceforge.net/sourceforge/nagios/nrpe-2.13.tar.gz

4. Nagios Plugins source for Linux:
http://prdownloads.sourceforge.net/sourceforge/nagiosplug/nagios-plugins-1.4.16.tar.gz