Network Management On the Cheap

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. As with all products, you get what you pay for, but this doesn't mean free products are risky. Most free network-management tools perform tasks so simple and so straightforward--pinging, looking up names, serving files--you can be confident they'll work. For this simple stuff, support just isn't that important.

But as you rely on deeper functionality, such as packet capture, decode and network-performance assessment, you'll need to look more closely at support. MRTG (Multi Router Traffic Grapher), which is free and graphs SNMP values, has a great support community. However, everyone within that community contributes only out of his or her good graces. So if you don't have the time, you'd better have the money to invest in a fully supported corporate (read: expensive) solution.

Cheap network utilities and network-management products are easy to find and easy to use. So why would anyone consider the big, expensive network-management suites from the likes of Computer Associates, IBM and BMC Software? It depends on your organization's goals. If the network is making money or directly supports money-making transactions, you probably have to bite the bullet and invest in a centralized relational database with common data formats and maintenance contracts--it will be worth the cost.

What's Crummy

Simple network-management utilities and tools can't handle growing networks nor survive major catastrophes in their operating environments. They have no common data store, distributed processing or redundancy. But the more strategic network-management products have become costly and difficult to implement in the attempt to solve those problems.

It's simpler to save gathered inventory data in a flat ASCII file, for instance, if all you need from the data store is a printout of devices found during a ping sweep. However, if the discovered network devices will be polled by an SNMP performance-management application and this information will be used to determine what devices need service contracts, the ability to share that data becomes valuable. It's easier to share using SQL queries than by building specific parses on data stored in a flat file; but implementing a SQL database costs more.

Another issue simple network-management tools don't address is distributed processing. Polling a device on a LAN for SNMP utilization and error information uses very little bandwidth. However, if the router, server or remote LAN is accessed over a WAN, even the small amount of bandwidth required for this retrieval may be too much. The more complex network-management products build specialized polling and compressed data-transport mechanisms to preserve the narrow WAN bandwidth.

Before you choose a direction, keep in mind that tools, whatever their cost, do not a network-management solution make. In the end, they're are only a small part of what enables good network management. The people who manage the tools matter most.

Bruce Boardman is executive editor of Network Computing. Write to him at [email protected].Post a comment or question on this story.