How to Test an Ethernet Cable

Last Updated: March 29, 2019

This wikiHow teaches you how to test an Ethernet cable. To test an Ethernet cable, you need a cable tester. There are different models of cable testers you can purchase. Some have a detachable receiver unit that you can use to test a cable across two rooms.

Steps

1
Purchase an Ethernet cable tester. There are many models you can purchase. Make sure it has a battery in it and power it on.
2
Plug one end of the cable into the transmit jack. The transmit jack on the tester maybe be labeled "TX".

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3
Plug the other end of the cable into the receiver jack.The receiver jack may be labeled "RX" on the device. Some testers have a detachable receiver you can use to test the cable across different rooms.^{[1]
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4
Check the lights on the tester. Most testers will have 2 sets of 8 LED lights that correspond to the 8 pins on the transmitting and receiving end of the Ethernet cable. There will also be a G light for the ground. It will test each pin one at a time. If all 8 pins light up on both ends, the cable is good. If any of the lights do not light up on either end, this indicates a short in the cable. Don't worry if the G light doesn't light up. If the lights on either end flash out of order, this indicates that you are testing a crossover cable. As long as all 8 lights flash, the cable is good.^{[2]
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Community Q&A

Question

If no lights are showing, is my cable tester broken?

Community Answer

Yes. Most likely, your tester isn't working.
Question

Is it possible that when using a tester, the cable checks as good, yet it does not work?

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Community Answer

Maybe. It is a possibility. The ethernet cable "could: work, but you never know until you try.
Question

I have 8 lights showing but my laptop says "cable not connected", so no signal. What is the issue?

Community Answer

Try to reconnect the cable again. Doing this may resolve your issue.