Zenoss - Open Source Network Monitoring Tool

Zenoss (Zenoss Core) is an open-source application, server, and network management platform based on the Zope application server. Released under the GNU General Public License (GPL) version 2, Zenoss Core provides a web interface that allows system administrators to monitor availability, inventory/configuration, performance, and events.

Cacti - Open Source Network Monitoring Tool

Cacti is an open-source, web-based network monitoring and graphing tool designed as a front-end application for the open-source, industry-standard data logging tool RRDtool. Cacti allows a user to poll services at predetermined intervals and graph the resulting data. It is generally used to graph time-series data of metrics such as CPU load and network bandwidth utilization. A common usage is to monitor network traffic by polling a network switch or router interface via simple network management protocol (SNMP).

Zabbix - Open Source Network Monitoring Tool

Zabbix is a network management system created by Alexei Vladishev. It is designed to monitor and track the status of various network services, servers, and other network hardware. It uses MySQL, PostgreSQL, SQLite, Oracle or IBM DB2 to store data. Its backend is written in C and the web frontend is written in PHP. Zabbix offers several monitoring options. Simple checks can verify the availability and responsiveness of standard services such as SMTP or HTTP without installing any software on the monitored host. A Zabbix agent can also be installed on UNIX and Windows hosts to monitor statistics such as CPU load, network utilization, disk space, etc. As an alternative to installing an agent on hosts, Zabbix includes support for monitoring via SNMP, TCP and ICMP checks, as well as over IPMI, JMX, SSH, telnet and using custom parameters. Zabbix supports a variety of real-time notification mechanisms, including XMPP.

The package includes Installation and basic configuration.

Nagios - Open Source Network Monitoring Tool

Nagios is a popular open source computer system monitor, network monitoring and infrastructure monitoring software application. Nagios offers complete monitoring and alerting for servers, switches, applications, and services and is considered the defacto industry standard in IT infrastructure monitoring. It watches hosts and services, alerting users when things go wrong and again when they get better. Nagios was originally designed to run under Linux, but also runs well on other Unix variants. It is free software, licensed under the terms of the GNU General Public License version 2 as published by the Free Software Foundation.