Nagios is a powerful network monitoring tool that helps you to ensure that your critical systems, applications and services are always up and running.
It provides features such as alerting, event handling and reporting. The Nagios Core is the heart of the application that contains the core monitoring engine and a basic web UI. On top of the Nagios Core, you are able to implement plugins that will allow you to monitor services, applications, and metrics, a chosen frontend as well as add-ons for data visualisation, graphs, load distribution, and MySQL database support, amongst others.
If you want to try out Nagios without needing to install and configure it from scratch, download Nagios XI and enable the free version. Nagios XI is the pre-configured enterprise class version built upon Nagios Core and is backed by a commercial company that offers support and additional features such as more plugins and advanced reporting. The free version of Nagios XI is ideal for smaller environments and will monitor up to seven nodes.