Cacti is a network graphing solution designed to harness the power of RRDTool's data storage and graphing functionality.

Munin is a networked resource monitoring tool that can help analyze resource trends.

Observium is a low-maintenance auto-discovering network monitoring platform supporting a wide range of device types, platforms and operating systems, etc.

Spiceworks is a professional network for the information technology (IT) industry.

Icinga is an open source computer system and network monitoring application.

Nagios known as Nagios Core, is a free and open source computer-software application that monitors systems, networks and infrastructure.

PRTG is a network monitoring tool that helps you to ensure that your computer systems are running smoothly and that no outages occur.

Zabbix is enterprise open source monitoring software for networks and applications.