Question Speed & Duplex Disconnect

Jul 4, 2021
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I have a Cat 6 50ft ethernet cable. My internet speed is 400mbps download and 20mbps upload. I switched my speed and duplex setting from auto negotiation to 1.0Gbps because I was being limited to 100mbps. It worked for about 3 days no issues, computer turned off about once a day. Then I came home today and it says Network Cable unplugged, checked the router, it handles up to 1Gbps for each port.
 

OrlyP

Prominent
Aug 20, 2020
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It's almost always the cable or more likely, the RJ45 connectors.

The fact that it won't auto-negotiate to 1gbps means that the line is 'dirty' or one of the pins aren't making positive contact.

Here are a few things I've done before that works... YMMV.

  1. Unplug and re-plug the RJ45 connectors and make sure that they're snug in their ports
  2. Use a copper steel brush and lightly brush the fingers on the RJ45 plug. This can help remove oxidation or dirt
  3. If the cable was DIY'd, try using a crimper to further push down on the pins so they bite the cables properly
  4. Cut off the RJ45 connectors and crimp in a new one
 
Reactions: bill001g
Yep, any cable that was working at gigabit and then went to fast ethernet is probably a bad cable. I've seen this happen on some of my oldest cables once they got past a certain age--just replace the cable with a good one, and watch out for the fakers because there are more of those than legit ones. Best way to get a legit one is to buy it at a local store since they would have too many angry customers in their face if they sold junk.
 

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