Most inexpensive network-management tools are simply monitoring tools. They provide information about the network via displays ranging from simple, system-tray pop-ups and blinking lights on a desktop to complex graphs showing minimum, maximum, average and threshold values over time. The less information you receive, the less you typically pay for the tool.

If you're looking for inexpensive network-monitoring and -management tools, consider offerings from the freeware and GNU communities, such as NetSCARF, Ethereal, Thingy, Tailinator and Cricket. Also, most commercial management vendors offer free product downloads for trials. Don't part with any dough until you have a good idea how much help a particular utility provides.

The range of inexpensive management tools available is as wide as the range of tools in a megasize Swiss Army knife; but do you need the saw blade with the toothpick, or will the tweezers and the can opener do? Luckily, these products come with just about every combination of features imaginable. You'll find inventory helpers, DNS managers, IP address figurers, switch and router watchers, event alarms, SNMP MIB everything, network diagrammers and full-blown packet analyzers.

From the Inside Out

Discovering a network is normally one of the first tasks network-management products attempt. Only after examining the network layout and the devices used on the network do they try to diagnose network problems. But getting the topology and inventory correct can be tricky.

To that end, network-management products use the Oreo approach, starting in the middle and working their way out. The creamy Layer 3 gets mapped with a ping sweep, then the tool moves outward, trying SNMP, TCP and UDP ports. The good tools will attempt to piece together a Layer 2 topology, mapping the MAC (Media Access Control) addresses attached to specific switch ports. Of course, in a shared-hub network, Layer 2 goes out the window, but even in all-switched networks, correctly identifying devices attached to specific ports isn't always possible. This is partly because a specific MAC address will most likely show up in a multiple-switches cache. If the device is supporting the Bridge MIB, it's possible for the software to figure out what's attached. Unfortunately, not all SNMP is created equal, and sometimes the information is reported incorrectly. I've yet to find network-management software, complex and expensive or cheap and simple, that gets these Layer 2 mappings right 100 percent of the time.

Additionally, no network tool can map the total physical layer "automagically." Most cable testers will map pin outs, cable length, physical path attenuation and cross talk. But they can't tell you what patch panel is used and what conduit the path takes--there's no replacement for those old-fashioned manual drawing tools.