CertiGuide to Network+  9  Chapter 0001:  LAN Cabling       9  IV  Coaxial Cable (Coax)

Coax Termination 1 2 Coax Cable – New Developments

When supporting 10Base2 and 10Base5 networks, you may occasionally run into cable-related difficulties that affect all or part of the network. Some of these include:

As noted above, each length of cable must be terminated at each end with a terminating resistor. If the terminator is not appropriately attached, or is missing, all workstations on that cable segment will (probably) lose network connectivity. They will be unable to reach neighboring workstations, and the rest of the network. To address this, re-attach or replace the terminator. (Review Figure 8, a few pages previous)

A 10Base2 or 10Base5 cable may experience a break, which may or may not be obvious. Excessive sharp bending of these coax cable varieties can affect their ability to carry a signal without a detectable break.

When this happens, all workstations connected to that cable segment usually lose network connectivity. To find cable break or termination problems, you can use a Time Domain Reflectometer (TDR) to measure electrical properties of the cable and identify issues. To address a cable break, replace the cable.

10Base5 network connections require a device known as a transceiver, which interfaces between the 10Base5 network cable and the workstation. Sometimes a transceiver malfunctions due to a hardware problem, or due to being improperly attached to the cable or the workstation, and it produces a high number of packets in a short window of time, clogging the network and causing an excessive number of collisions on the network. This phenomenon is known as jabbering. To find the transceiver at fault, you might go from workstation to workstation, checking each transceiver for a transmit light that never seems to go off. If that’s too big a job on a larger network, again, you can use a TDR to locate the area of the problem.

Coax Termination 1 2 Coax Cable – New Developments