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LAN cable burnout

Drashna Jaelre

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Just out of curiousity, does anyone besides myself experience?


I just replaced the LAN cable (cat 5e) that connects my Sophos UTM device to the cable modem as I was having some serious connectivity issues. As soon as I did, not only was everything back to normal, but even faster than before.


The cable wasn't kinked, nor damaged in any visible way. I had already rebooted every device on the network, and had reseated cables. 



And this is definitely not the first time I've experienced this... 

It may be a good time to get a good cable tester soon.

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I've had Cat 5 cable go "bad" in the long run from the basement to the 2nd floor of my house


 impurities in the metal  or other defects will  reduce the ductility of the wire and could lead to fractures over time


In my case, it failed at a 90 deg  bend  not far from  my garage door opener  


I either damaged it when I first installed it or damaged it a bit then the repeated vibration from the garage door opener caused it to fail after ~ 5 years


When replacing it,  I made sure to stay away from it when I ran the wire thru the attic over the garage.   also made sure that I had at least a 2" radius on any bend in the wire run.


better quality cable will stay flexible and have less chance of breaking ( not just heavier gauge wire, better quality wire and insulation)

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One major way cables 'go bad' is that the connections between the RJ45 jack pins and the actual wire in the cables weaken, usually from corrosion of the copper. Often, simply re-crimping the existing RJ45 connector will restore the connectivity. At some point though, it becomes necessary to cut off the connector and crimp on a new one (one main reason to leave a little slack when making cables).


A common cause of RJ45/copper wire connectivity issues is using the wrong kind of RJ45 connector. There are different ones for solid wire (plenum/riser/structural) versus stranded wire (patch cable). I believe there is now a connector that is supposed to be good for both types of cable, but I've never used them


Yes, it is very important to avoid bending cables in too small a radius. I try to never bend cables in a 90 degree or greater curve. If you are going to make bends that sharp then be sure to allow at least a 6" radius.


It's also very important to avoid too much force when pulling cables. If you pull too hard you can actually stretch the copper and make it thinner, which alters the electrical characteristics of the cabling.


Finally, all of these things are very good reasons to have a good Ethernet cable tester. I don't mean a wire map checker. These are the cheap devices you can find online, often for under $100. They are fine for verifying that a cable has been properly wired, but they can't do anything about cable performance/capability. The cheapest good quality tester I know of that can actually test cable performance is the one from Byte Brothers, and it costs around $600US.

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I had some bad cable last week, I have no idea how long it had been sat with the supplier but I imagine the short length we needed was a left over bit from somewhere rather than out of a new box, in some places when I was making up the end of the cable the copper wire was bare...

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I haven't really found that the age of a cable is much of a factor, as long as the cable was good quality to begin with. What I have done is cut the end of a cable back a few inches before crimping on a connector, just to be sure any copper that might have corrosion in it has been removed.


The most important factor to me is to be able to test the cable after it's made. That's really the only way to know for sure how good a cable is.

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