I will also delve into a somewhat controversial subject surrounding protocol analyzers: Are expert systems truly that helpful?

Cable Testers Grow Up High-end cable testers have evolved to the point of testing nearly every parameter imaginable in a piece of cable: short, open, length, near-end cross talk (NEXT), split-pair, attenuation, cable ID and Category 3/4/5 certification, to name just a few. What more could a network engineer want?

One of the really cool things about a cable tester is its high degree of portability: It is a device you can hold in one hand, it runs on batteries and it doesn't take up much room in your network analysis bag of tricks. If there are media problems on a segment, as noted on your analyzer or SNMP p robe as Cyclic Redundancy Check (CRC) errors (on Ethernet) or line errors (on Token-Ring), th e cable tester is invaluable in helping you pinpoint the cause of the problem. Since the cable tester is easy to carry around, why not add some testing capabilities? This is what many of the leading tester vendors have done.

With the addition of a microprocessor, some memory and firmware, cable testers can transmit and receive packets. The diminutive processing capability, screen size and limited keyboard prevent the cable tester from becoming a full-blown protocol analyzer, but it can perform proactive testing and data querying--something most protocol analyzers don't perform. The testers typically let you perform ping tests, identify active servers, display network utilization and error counts, and show top senders.

These handheld network testers are filling a niche between cable testers and protocol analyzers. With the added ping capability, you can ping a device for its existence and measure round-trip delay without having to go to a workstation or SNMP console--now it's done from the convenience of a wiring closet. Some of the tools included in a few of these handheld gems also let you perform a traceroute to check the path and response time for each hop.

Fluke Corp.'s Enterprise LANMeter (it's actually half the size of a notebook, but you can still hold it in one hand!) goes one step further by letting you query SNMP probes and agents. In essence, the LANMeter is a mini-SNMP console. After troubleshooting some problems on a client's network recently, I decided to do a little proactive analysis by probing the routers in various locations around the campus and nationwide.

Armed with network documentation, but not the SNMP community name, I obtained the community name the lazy way--by waiting for an SNMP trap packet captured by the protocol analyzer. It took only a minute or two to get one, then I set the community name in the LANMeter and was able to query the SNMP management information base (MIB) inform ation from any router on the network.

To download an Adobe Acrobat .pdf format version of the Network Analyzer Buyer's Guide charts, click here.