Networking: A Beginner's Guide
Troubleshooting Star Networks
Star networks are the easiest to troubleshoot. Because each node is on its own network
cable leading to the hub, you can often quickly isolate the problem to several lengths
If you're having trouble with a node on a star topology network, first determine if
something is wrong with the computer or the cabling. Move the computer to a different
location in the building and see if the same problems occur. If they do, then it's a sure
bet the problem is in the computer, such as a failing NIC.
If the computer has normal network performance in a different location, try
replacing the patch cable leading from the node to the wall. These cables can often
become slightly damaged as furniture or computers are moved around.
Next, in the wiring closet, you can try connecting the patch panel from the node's
location to a different port on the hub using a different patch cable. While wiring closet
patch panels are less likely to fail, because they aren't moved around much, they can
still have poor connections or wiring that can become problematic over time.
Finally, if you have eliminated all other factors, consider replacing the cable
leading from the wiring closet to the node's location. At this point, having a qualified
network cabling contractor to assist you can be extremely helpful. The contractor has
equipment to test the cable in the wall and to determine if it's bad before pulling a
replacement cable through the building. For troubleshooting help, you should expect
to pay around $150 for a contractor to come out and test a length of cable. If the
contractor must pull a new cable all the way to the location, you'll also need to pay for
labor and materials for that work.
Troubleshooting Coaxial Networks
Coaxial networks can be difficult to troubleshoot because many nodes share a single
segment of the network. Usually, a problem in one part of the segment affects all nodes
on the segment similarly.
By far, the most common problem on coaxial networks is loss of network
connectivity for all the nodes in a segment. Someone disconnecting the network cable
so it is not a continuous run invariably causes this loss. Find out who is moving to
another office, rearranging an office, painting an office, or performing other work of
this type is in the building. The chances are excellent the problem is there. If this fails,
then the troubleshooting job becomes much more difficult.
To track down cable breaks that aren't obvious, you can try using a coaxial cable
scanner. These are hand-held instruments that can be attached to a coaxial network
cable to detect how far along the cable shorts or breaks are occurring. Keep attaching
the cable scanner to the network cable in different locations until you can track down
Another approach is to test with an extra terminator for the network. Disconnect
the cable in a particular location and attach the terminator. See if the computers on
the new, smaller segment can log in to a server. (A server must be available in the
same segment; otherwise, you can use the PING command, if you're using the TCP/IP