Network Cable Passes Test But No Link Light
Hi folks!
Just ran a new run of CAT6 UTP Plenum cable. The cable is punched down into keystone jacks at either end, and then has a pre-made CAT6 patch cable connected at each end.
If I connected a basic cable tester to either end, it tests perfectly. All eight lights come on, in the proper sequence, indicating that all eight wires are in the proper order and getting a signal through. However, if you plug a computer, switch, or any other network device in, you get nothing. Not even so much as a link light.
So I'm confused. I've never seen a cable where you could get a perfect test and then not even get a link light.
Any thoughts?
Thanks,
Ithizar
Just ran a new run of CAT6 UTP Plenum cable. The cable is punched down into keystone jacks at either end, and then has a pre-made CAT6 patch cable connected at each end.
If I connected a basic cable tester to either end, it tests perfectly. All eight lights come on, in the proper sequence, indicating that all eight wires are in the proper order and getting a signal through. However, if you plug a computer, switch, or any other network device in, you get nothing. Not even so much as a link light.
So I'm confused. I've never seen a cable where you could get a perfect test and then not even get a link light.
Any thoughts?
Thanks,
Ithizar
Scott C
Is the NIC you're plugging it into good? Have you tried a different computer? Check the port that the cable is plugged into. It might not be an issue with the cable.
I would move that cable to another Pc and test it. There may be a problem on that POc like the Nic beiung disabled, dns server addresses being wrong, possibly the IP needs to be released and renewed..
Verify the PC gets it's IP dymanicly and go to Start/Run type in CMD
In the box type
IPCONFIG /release
IPCONFIG /renew
IPCONFIG /registerdns
try pinging a server in your facility
ping Yahoo.com
Verify the PC gets it's IP dymanicly and go to Start/Run type in CMD
In the box type
IPCONFIG /release
IPCONFIG /renew
IPCONFIG /registerdns
try pinging a server in your facility
ping Yahoo.com
ASKER
Thanks to both of you, but I have already ruled out it being an issue with the computer's hardware.
First, I took the computer in question and moved it to another room, and when connected I get a link light and full network access. Then, I brought a different computer into the office in question and got the same behavior with no link light and no access. On the other end of the cable, I also tried connecting it to more than one switch, always with the same result.
It seems that the problem has to be with the cable itself, but I just can't figure out what sort of problem could allow it to pass the test with the network tester but not even generate so much as a link light on the devices.
First, I took the computer in question and moved it to another room, and when connected I get a link light and full network access. Then, I brought a different computer into the office in question and got the same behavior with no link light and no access. On the other end of the cable, I also tried connecting it to more than one switch, always with the same result.
It seems that the problem has to be with the cable itself, but I just can't figure out what sort of problem could allow it to pass the test with the network tester but not even generate so much as a link light on the devices.
Did you check or try switching out the pre-made cables at each end?
ASKER CERTIFIED SOLUTION
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ASKER
When I say I am using a network tester to test this, I mean that I have patch cables plugged into the jacks on either end and I am plugging the tester into the end of each patch cable. So that cable run, as being tested, is:
Tester -> Patch Cable -> Wall Jack -> New Cable Run -> Wall Jack -> Patch Cable -> Tester
If I am getting a perfect test on all eight wires through that entire path, that would seem to indicate that both the patch cables and the wall jacks are okay, wouldn't it?
Tester -> Patch Cable -> Wall Jack -> New Cable Run -> Wall Jack -> Patch Cable -> Tester
If I am getting a perfect test on all eight wires through that entire path, that would seem to indicate that both the patch cables and the wall jacks are okay, wouldn't it?
It would seem that way but it wouldn't hurt to swap them out one at a time for testing.
This definitely is a layer 1 issue.
There is no connection detection!
Connections will be detected whether there is an ip address or not.
A crossover cable between a computer and a switch will not give you any light!
A straight cable between a switch and a switch won't either
like + like = crossover, like + unlike = straight
(There are uncommon exceptions to this rule though)
Also, confirm that the switchports connected to the switch ends of cable are not shut down.
If these don't apply, then you have a wrong or bad cable.
It's either the testers are wrong or your connections are wrong
There is no connection detection!
Connections will be detected whether there is an ip address or not.
A crossover cable between a computer and a switch will not give you any light!
A straight cable between a switch and a switch won't either
like + like = crossover, like + unlike = straight
(There are uncommon exceptions to this rule though)
Also, confirm that the switchports connected to the switch ends of cable are not shut down.
If these don't apply, then you have a wrong or bad cable.
It's either the testers are wrong or your connections are wrong
Perhaps they got the pairs wrong.
The cable has 4 twisted pairs, that need to be connected to the right pins in the plugs.
Maybe they got the 8 pins in the same order at both ends - but they did not get the pairs right. The "twist" is very important for the signal. Possibly your tester is only testing the order of the pins.
The cable has 4 twisted pairs, that need to be connected to the right pins in the plugs.
Maybe they got the 8 pins in the same order at both ends - but they did not get the pairs right. The "twist" is very important for the signal. Possibly your tester is only testing the order of the pins.