System administrators looking for an open source alternative to expensive network management and monitoring application suites might find the Nagios software suite worthy of a test drive.

Nagios is an open source software package consisting of a monitoring daemon and monitoring plug-ins, which can be used to monitor the health of hosts, such as servers, routers and other network nodes, as well as gauging the availability of general network services such as POP, SMTP and HTTP, among others. The system can also be configured to send notifications via e-mail, pager or cell phone text messaging during network events, or warning of conditions that could lead to an outage.

The software package was written with Linux in mind, but should run well on most Unix platforms, the developers say. A Web interface is used to monitor and configure the system, and to access its log files. The plug-in based architecture of the package allows it to handle a wide variety of monitoring devices. Most recently, heating, air conditioning, and ventilation (HVAC) sensory vendor ESensors released a plug-in for its products, allowing users to monitor environmental data - server room or wiring closet temperature and humidity, for example - in Nagios.

Some buzz has built around Nagios over the last few years, as many large enterprise firms and organizations - such as AOL, jet-maker Lear, TicketMaster, TimeWarner and the Univeristy of Wisconsin - have quietly used Nagios for monitoring network availability and for detecting server outages. 

One IT executive at a multi-national biotech company, who wished not to be named, told me he is seriously considering using Nagios as a complete replacement for his Tivoli-based network management software.

"If I continue my Tivoli license, I'm looking at about a $1.5 million-a-year contract," said this network administrator. With Nagios, he says, "I can probably get away with 80% of what Tivoli does; we can just develop our own applications to do the other 20%."