Weird wiring issue with Cat 5e and Keystone jacks

[Kuroukaze]

Hello everyone!

My problem is I just set up a wall plate with 3 keystone jacks wired back to my patch pannel set up. Right now the cables plug directly into my Linksys Etherfast 10/100 Autosensing 16 port hub. The cables at the wall plate have Cat 5/6 keystone jacks, though I don't know the company (they were aquired for me). Each cable at the jack is labeled alphabetically, A, B, and C respectivly.

Here's my problem; connection A works fine, dosn't have any problems, and can access my network. Connections B and C when tested with a signal tester can carry the electricity needed to power various LED contraptions that I have from the previous IT administrator here, and test fine with a cable tester. When connected to a computer though the comptuer will tell me "Network Connected at 100.00 Mbs" then 2 seconds later it will replace that message with "Cable disconnected". Then it repeats. It goes on like that all the time, no pause or variation.

I have tried moving the cables around on the hub to see if it was a bad port. A still worked, B and C did not. I have already re-wired it once, it was having a similar problem before (again A worked, B and C did not). All the wiring goes down the same conduit in the wall and through the ceiling, and they all are about the same length. I have checked the physical connectors probably a hundred times to ensure that they were connected properly.

Has anyone ever had a problem like this before? What can I do to troubleshoot?

Thanks for any help you can offer

 

[phoneguy55]

How are your terminations 568A or B. I saw once that someone tried to run 100 MEG on USOC terminations and that caused the problem you are decribing.

 

[wires]

Sounds like it could be split pairs or spliced/damaged cables.

For most ethernet to work you need two pairs and each wire in the pair must be twisted with it's mate. Looking at a network cable plug with the latch down one pair is at pins 1&2 and the other is at pins 3&6. If the original installer followed common standards the white orange/orange and white green/green pairs will be on those pins.

The common wiring schemes are called 568A and 568B. Here are the pin outs:

568A
w/green
green
w/orange
blue
w/blue
orange
w/brown
brown

568B
w/orange
orange
w/green
blue
w/blue
green
w/brown
brown

Best of luck.

 

[Kuroukaze]

I've got the cables connected with the 568B standard on both ends. As far as I can tell the cable wasn't damaged, as my cable testers don't return any errors (I plan on getting another one just in case mine isn't working...it's second hand from the last administrator).

 

[skip555]

sounds like the cables have a plug crimped to them and are plugged direcly into the hub ?

thats a bad practice , terminate the hub end of the cable into a a keysotne jack or a patch panel and then use premade patch cords to go the hub

 

[Jtodd]

This could be a split pair issue. Basic continuity testers will not catch this, as they only test each individual conductor, not the pair unit.
Check and make sure that the white/green goes with green, not the blue or white/blue with the green. Most common mistake with a split pair.

Justin T. Clausen
Physical Layer Implementation
California State University, Monterey Bay

 

[ISDNman]

Are you sure all three cables are Cat 5e?

Best of luck...

 

[mikeydidit]

I agree with ship. Terminate these on a patch panel and use short premade patch cables and you can at least rule out the plugs on the ends of the cables. I would also look at the jacks closely to make sure they are rated for Cat 5 or Cat 6.

Mike Jones
Louisiana State University Health Sciences center

 

[oldtimerbob]

It could be something simple like a bad or damaged patch cord at the station end?

 

[exverizon]

All keystone jacks are not designed with the same puchdown layout. I've got a bag of 'em I bought together and some are of one revision, some of another. When I looked closely at the color keys printed on them, I found some pairs turned over or arranged in another pattern...even within the A or B scheme. Assuming you've verified this EXACTLY for each jack, and the patch cables on both ends are known good, there's little else left but repulling the two cables that are in trouble. Sometimes too much pull force can damage--just a bit--the conductors. Specs say 25 lbs of pull is the limit, although we all probably exceed that regularly. There's not much else that can be wrong. It's all just hardware.