Random cat5 issue

[Oaktech]

Someone has done a hatchet job on some cat 5 when they installed it.

 

A new cabinet was installed with a single 24port poe switch in it. No dedicated uplink was run in. A point from the new cabinet was put adjacent to the nearest existing point and the existing point removed, an RJ45 put on the cable and plugged into the new point. (nice).

 

It's only ever operated at 100mb apparently but over night it seems to have randomly failed, but in an obscure way.

 

I've only got a pinout tester rather than a proper certifier, but the whole length tests OK pin for pin.

 

If you plug the whole length into the switches there is no connection.

If you plug a laptop into either end of the length with the other end plugged into a switch, you get nothing.

If you split the length where they've done the nasty join and plug a laptop into either part of the link you get a connection back to a switch.

 

We've measured the distance with a trundle wheel and it's 57m.

 

I'm out of ideas now as to what on earth is going on. Anyone got a clue?

[ITGURU]

Someone has done a hatchet job on some cat 5 when they installed it.

 

A new cabinet was installed with a single 24port poe switch in it. No dedicated uplink was run in. A point from the new cabinet was put adjacent to the nearest existing point and the existing point removed, an RJ45 put on the cable and plugged into the new point. (nice).

 

It's only ever operated at 100mb apparently but over night it seems to have randomly failed, but in an obscure way.

 

I've only got a pinout tester rather than a proper certifier, but the whole length tests OK pin for pin.

 

If you plug the whole length into the switches there is no connection.

If you plug a laptop into either end of the length with the other end plugged into a switch, you get nothing.

If you split the length where they've done the nasty join and plug a laptop into either part of the link you get a connection back to a switch.

 

We've measured the distance with a trundle wheel and it's 57m.

 

I'm out of ideas now as to what on earth is going on. Anyone got a clue?

We've had a similar issue before with our Digital Signage before - entire run didn't work, split it where we thought there was an issue, both side of the slip worked and tested fine

 

Even though a cable tests fine, if your going switch to switch it may not be able to auto-negotiate. Perhaps try forcing each end of the link to 10 or 100meg just in case?

[jinnantonnixx]

The cable might be wired up in an electrically correct way (the continuity is good), but are the pairs wound properly?

Check the colour-to-pin layout.

 

If the pins & colours don't match this guide, you've effectively unwound the cable pairs.

 

Many moons ago, we bought some patch cables from a cowboy outfit and they wired them up the wrong way. It passed the normal checks, but failed when used in the real world. The pairing is crucial as the cables are unshielded, so rely on the pairings' phase to cancel out interference.

 

If that checks out, it could be that the cables runs over a noisy object, like a fluorescent light.

http://www.dslreports.com/forum/r4634184-Distance-between-Cat-5-and-Fluorescent-Lighting

Edited March 9, 2017 by jinnantonnixx

[gh5000]

Put a switch in the middle to pair the two cables as a stop gap if it's essential until you get to easter holidays to do some proper tests.

[Oaktech]

The cable might be wired up in an electrically correct way (the continuity is good), but are the pairs wound properly?

Check the colour-to-pin layout.

[ATTACH=CONFIG]42033[/ATTACH]

 

If the pins & colours don't match this guide, you've effectively unwound the cable pairs.

 

Many moons ago, we bought some patch cables from a cowboy outfit and they wired them up the wrong way. It passed the normal checks, but failed when used in the real world. The pairing is crucial as the cables are unshielded, so rely on the pairings' phase to cancel out interference.

 

If that checks out, it could be that the cables runs over a noisy object, like a fluorescent light.

Distance between Cat 5 and Fluorescent Lighting - Networking | DSLReports Forums

 

I've reterminated everything now and I still have no joy!

 

I'm going to run a new cable to it because it's not well done right now.

[AlanD]

I remember a similar issue I had....and a simple circuit continuity tester did not pick up the fact that two cables where shorting....but pin to pin everything looked fine.

 

...but you are certain its not the switch ports themselves "black listing" the MAC address is some way? I'll assume you tried connecting a laptop to one end....

[Oaktech]

It would appear that it was something to do with the join. I've put an IDC joint in the middle, taking out the plug and socket and suddenly everything has sprung into life at full gigabit...