How to Test an RJ45 Connection

This simple testing technique is a great way to check the connection quality of RJ45 terminations on new CAT5, CAT5e and CAT6 LAN cables, and can also be helpful in troubleshooting the data transmission problems in existing network cabling. Please Note: The tester shown in the images below is no longer available, but you can check out our line of LAN cable testers here

Project Checklist

Experience Level: Intermediate

Time Required: 2 minutes

Steps: 4

Supplies: LAN cable tester or Multi-Network modular cable tester

Budget Estimate: $41 - $128



LAN cable tester

Turn the testing unit on.


RJ-45 cable plugged into LAN tester

Plug the ends of your RJ45-terminated cable into the tester's two ports … it doesn't matter what order you do this in.


turning the cable tester on

Depending on which tester you use, the test function will be either manual or automatic. If you're using the automatic test mode, simply push the button and let the unit do its work. If you need to use a manual mode, simply hit the test button repeatedly to advance through all 8 wires.


indicator lights on the LAN cable tester

You'll see two separate bars of indicators, each with 8 lights. Watch these indicator lights as the test sequence is completed, wire-by-wire. If both the “input” and “output” indicators for each wire are brightly lit, then you know that optimum connection has been made. A dim light indicates poor connection, and no light at all lets you know that connection is not being made.

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