#9 Nagios:

Nagios is an open source network monitoring software that can also provide a bit of infrastructural check in system software. Nagios monitors and alerts servers, switches and applications. Enterprises find this software useful as it alerts users when things go wrong and alert them again when the crisis is being resolved. Developed originally under the name NetSaint, Nagios is written and maintained by Ethan Galstad and a group of developers. The software got its initial release in the year 1999.

#8 Munin:

Munin is a network resource monitoring tool that helps enterprises analyze the latest resource trends. The software provides results as easy graphs through a web interface. One of its main emphases is on the plug and play capabilities of a system. Munin help supporters to monitor the performance of their computers, networks, LANs, and applications. This software is primarily written in Perl language and uses RRD tool for monitoring. The software also monitors resource breakouts within a network.