Weird ethernet (Cat5e) wiring issue...

[Epsil0n00]

I am having a weird wiring issue at work with a particular Cat5e installation. Here's the scenario:

I asked our wiring guy to pull 2 new wires to a room and mount them to jacks on a wall plate, and connect these lines to our patch-block on the other end. Well, he didn't know what he was doing and punched the lines down into a phone block in the wrong area of the building... I found out what he did and had him correct the issue...

He disconnected the lines from the wrong block and punched them into the correct network patch-block. One of the lines was long enough to go the full run, the other line had to be spliced. I patched both ports into our switch and proceeded to try and hookup a desktop computer to the wall jacks... here is where things get weird.

The desktop computer, a 4-year-old Gateway desktop, doesn't recognize the ethernet network signal... there's no link lights on the NIC, nothing. I tested the computer with another NIC and it didn't work either. So, I figured it had to be the wiring still. I tested both ports with a 1-year-old IBM ThinkPad laptop and it recognizes the ethernet connection just fine--link lights, 100mbps connection recognized in Windows, everything is fine! I began to think that I was going crazy... so I tested the desktop in another location with different AC power and different ethernet connections and it works fine.

Why would an ethernet Cat5e signal be recognized by a new laptop, but not by an old desktop? This wiring install shouldn't be any different than the rest of our network, but obviously something isn't quite right. Both the laptop and the desktop have 100mpbs NICs... I'm stumped!

Any insight!?
Thanks!
Epsil0n

 

[bob4432]

tagged to learn why....sorry i can't help but this is interesting...fire the cable puller

 

[cubby1223]

I'd force the nic to 10mbit to test out.

 

[SlitheryDee]

Maybe the problem is with the desktop and not the wiring.

 

[Epsil0n00]

Originally posted by: SlitheryDee
Maybe the problem is with the desktop and not the wiring.

As I said, I also thought that the desktop might be the source of the problems... however, I have tested this desktop in another location (a different network connection) and the NIC works fine. I ran an extension cord to this desktop to make sure the AC power was good, but that didn't help the problem. I have tested all the variables with at least one other known-working component and the only variable that I have been unable to verify is the wiring that was recently installed.

The wiring guy is going to pull new wires, but we're both very curious to figure out what would cause it to work with a new laptop, but not with an older desktop.

 

[bob4432]

maybe when the splice was made it made the signal just a little bit weaker and the nic is not as forgiving as a newer one? was the other nic you tried the same type or a different type? i really don't know. when he pulls the new cable, let us know if that fixes it.

 

[Epsil0n00]

I had also thought about the splice... but he claims that only one of the lines was spliced--the other one went directly with no interruption... but neither one works. Both of the lines work fine on the laptop, but not on the desktop... very strange stuff...

I have no clue...

 

[bob4432]

Originally posted by: Epsil0n00
I had also thought about the splice... but he claims that only one of the lines was spliced--the other one went directly with no interruption... but neither one works. Both of the lines work fine on the laptop, but not on the desktop... very strange stuff...

I have no clue...

does the cable go over 100Meters? next to anything that my induce some interference, maybe some high voltage lighting? have them in the correct order 568A or 568B (from what i have read this scheme is to reduce induced noise, but not sure as i usually only run at most 100FT), i am just throwing things out there as i am really stumped.