Understanding Network Cabling
protocol on your computers, and try to ping another workstation in the complete
segment.) If they can log in, then you know the problem is further on along the cable.
Move to a new location, attach the extra terminator, and try again. Eventually, you
will find two nearby locations where the terminator will allow the network to work
in one spot but not in the next spot. You should find the cable problem somewhere
between those two node locations. This approach requires patience, but it works
fine in a pinch.
More troublesome still on coaxial networks is a problem that is causing poor
network performance, but not causing any nodes to actually disconnect from the
network. Such problems are often intermittent and not easy to find with a cable
scanner. When you have this type of problem, your best approach is to come up with
a test that can quickly tell you how fast the nodes are communicating with the network.
For example, you can time how long it takes to copy a particular file from the server.
Next, use a terminator to close off a large part of the segment and perform the test
again. Keep moving the terminator and retrying the test until you discover which part
of the cable slows down network performance on the segment. Then either replace all
those portions or narrow your search further. This type of problem is usually caused
by a poor connection in one of the male cable-end BNC connectors, although a flaky
T-connector or barrel connector can also be the culprit. It's usually fastest--providing
you narrow the problem to a small enough area--to simply replace all the cable and
connectors in that location.
Having a second person help you troubleshoot coaxial cable problems makes the
job much easier. One person remains in a fixed location at one end of the segment
with a test computer, and the other person moves from location to location with a
terminator. While the mobile troubleshooter maps out parts of the segment with the
terminator, the stationary person can quickly test to see if any individual parts of
the segment prove to be a source of the problem (communicating via a cell phone or
Before going to the trouble of pulling a new section of cable through the wall or replacing
various cables and connectors, try simply running an extra cable from one location to another, such
as out the door of one room, down the hallway, and into the room of another. Then test to see if this
"mapping out" of the suspect portion of the segment fixes the problem. If it does, go ahead and have
a new cable run in the walls. If the problem is still there, you need to look further before replacing
cable and connectors.
As a general rule, troubleshooting cable problems requires a careful, step-by-step
approach and patience. For coaxial cable systems, troubleshooting is made more
difficult because a lot of network users are breathing down your neck while you're
trying to concentrate and find the problem. You're lucky if you can find a coaxial
network problem and solve it within an hour. Some problems may take several hours
(or more) to resolve.