Testing Network Cables - A Primer

Networking cable, it comes in a single flavor, a Cat5e cable with a very distinct connector. Such a cable is a hardy piece of technology; it takes an extraordinary amount of problems to cause a failure in the line. It’s the same idea as a powerline suddenly not working anymore inside your home – it just doesn’t happen very often. But what about when you’re sure that your precious Cat5e cable has finally gone to that big spare parts box in the sky?

1. Connect the cable to the router and turn on the router.

2. Next, connect the Cat5e cable attached to the router to a testing PC.

3. The router has an IP address to connect through – type that into your web browser.

4. If your web browser is able to access your router through the IP address in the PC, congratulations! Your cable is working properly.

5. If you’re still worried about the cable not working properly, almost every router has a cable testing application that will show which cables are making the full duplex connection.

1. Suppose you fail the router test, what next?

2. Test the cable through the modem without a router in the mix, this should help you eliminate the modem as a potential source of problems.

3. Connect the cable to the modem and the other end to the computer.

4. Simply use the “connect to” feature of your Windows PC and connect using the network credentials.

5. Once connected, open your Internet browser, navigate to http://www.google.com and see if the website opens up.

6. If the website connects, congratulations, your cable works and you’re having a problem with your router.

1. If you fail the router and the modem test, it’s time to take more drastic measures.

2. Using an ohmmeter, connect two points on the Cat5e cable and check to see if there is resistance in the wire.

3. The ohmmeter shouldn’t be set too high, the internal resistance of the wire isn’t too great than a few Ohms.

4. If the wire on the ohmmeter moves, or the digital display reads anything other than “N/A” or blank, then your wire is working and the problem is either in your router or modem.

This process you just underwent is the same process you underwent in High School Science Lab, a process of elimination by “scientific means”. You’re just eliminating variables other than the wire itself by testing both the router and modem independently. And because this system works in a chain of command (cable -> router -> modem), it’s easier to test by elimination than any other way.