Several open source networking vendors offer free tools that conform to the GNU licensing strategy and whose source code is readily downloadable on the Internet.

If you hate to spend money, if you embrace the tenets of the Free Software Foundation, or if you have programming skills that you can devote to customizing and maintaining your own networking tools, then one of the three open source network-management tools we tested might be right for you.

At any price and in any form, the perfect management and monitoring tool efficiently and accurately discovers servers, clients, routers, switches and other devices.

It displays a map of the discovered nodes. It checks for connectivity problems and it notices performance problems. It alerts you via e-mail or pager, and it can escalate its alerts by e-mailing or paging multiple people until the problem's fixed.

It can in some cases automatically solve a problem by restarting a program, running a script or triggering an external program. It produces reports that show network health, measure use over time and forecast trends to help you plan the network’s future capacities.

The perfect monitoring tool is reliable, secure and easy to use. The perfect open source monitoring tool is easy to extend and enhance via custom programming.

To see how open source vendors measure up to these standards, we invited them to submit their products to our Alabama lab for testing. With permission from the vendors, we downloaded Zenoss's Zenoss Core, Hyperic's Hyperic HQ and GroundWork Open Source's GroundWork Monitor.

We tested these open source tools using the same methodology (see How we tested open source management products) we used to test commercial midtier network-management products last month).

Our Clear Choice award for best open source network monitoring and management tool goes to Zenoss Core. It gave us accurate discovery as well as superior monitoring of a wide range of devices, servers and applications. It was easy to use and the Zenoss Core source code is eminently extendable.

Product Zenoss Core Hyperic HQ GroundWork Monitor Vendor Zenoss Hyperic GroundWork Open Source   Price as tested Software cost is free, support starts at $3,300 per year. Software cost is free, support starts at $120 per CPU socket pair. Software cost is free, support starts at $8,000 per year for GroundWork Monitor for Small Business. Pros Excellent discovery of network resources; intuitive user interface. Impressive, complex thresholds; good reports. Good, basic network monitoring. Cons Needs a visual design environment for customizing reports. Remediation is a very manual process. Lacks dashboards; no ability to track Service Level Agreements. Score 4.0 3.6 3.1 The breakdown  Zenoss Core Hyperic HQ GroundWork Monitor Monitoring 20% 4 4 3 Reporting 20% 4 4 3 Ease of use 20% 4 3 3 Notifications 20% 4 3 3 Corrective actions 10% 4 4 3 Installation and documentation 10% 4 4 4 TOTAL SCORE 4.0 3.6 3.1 Scoring Key: 5: Exceptional; 4: Very good; 3: Average; 2: Below average; 1: Subpar or not available

Click to see: Test results compared