• Volt-ohmmeters, digital multimeters, and cable testers are useful in testing the physical connectivity of a cable plant.
• Time domain reflectors (TDRs) and optical time domain reflectors (OTDRs) are devices that assist in the location of cable breaks, impedance mismatches, and other physical cable plant problems.
• Breakout boxes and fox boxes are useful for troubleshooting problems in peripheral interfaces.
• Network analyzers decode problems at all seven OSI layers. Problems can be identified automatically in real-time, to provide a clear view of network activity and can categorize them based on the most critical problems.

Volt-ohmmeters and digital multimeters are at the low end of the spectrum for cable testing tools . These devices measure parameters such as AC and DC voltage, current, resistance, capacitance, and continuity. A cable tester might be able to perform the following functions:

• Test and report on cable conditions, including NEXT, attenuation, and noise
• Perform time domain reflectometry, traffic-monitoring, and wire-map functions
• Display MAC layer information about LAN traffic, provide statistics such as network utilization and packet error rates, and perform limited protocol testing, such as TCP/IP ping tests

Similar testing equipment is available for fiber-optic cable. Because of the relatively high cost of fiber optic cable and its installation, it should be tested both before installation, which is also referred to as on-the-reel testing, and after installation. Continuity testing of the fiber requires either a visible light source, or a Reflectometer, and is used with power meters that measure the same light wavelengths, test attenuation, and return loss in the fiber.

The cable tester shown in Figure is the Fluke 620 LAN CableMeter. This cable tester is used in many Cisco Academies to verify connectivity of all LAN cable types. It can measure cable length or the distance to a defect. It is also used to test for faults, such as: opens, shorts, reversed, crossed, or split pairs.

At the top end of the cable-testing spectrum are TDRs. These devices can quickly locate open and short circuits, crimps, kinks, sharp bends, impedance mismatches, and other defects in copper cables. Some TDRs can also calculate the propagation rate based on a configured cable length.

Network monitors continuously track packets crossing a network. This provides an accurate picture of network activity at any moment, or a historical record of network activity over a period of time. Network monitors do not decode the contents of frames. They are useful for finding the baseline of a network. Sampling the activity on a network over a period of time to establish a normal performance profile provides the baseline. The Fluke OptiView is an example of a network monitor. The OptiView detects devices on the network, lists possible problems, and also discovers network segments and Net BIOS domains.
 

Web Links Fluke http://www.flukenetworks.com