One 100Mb port !

Following on from Gigabit Ethernet reporting as 100 meg I have finished terminating mine here.

All of them register as Gigabit with transfer rates of around 700Mb - probably limited by the discs rather than the cabling. Except one circuit which terminates at a location where I have four individual sockets. That one will only work as 100Mb and the cables all follow the same route.

So, I remade the terminations at both ends, changed patch leads, changed sockets on the switch, tried a second PC all to no avail. Put a patch lead from that one to an adjacent socket and at the patch panel started to check continuity ... and what do I find? Continuity on 7 but on pin 2 - nothing! Somewhere the conductor has broken.

I decided I would have to live with it as running a new cable would not be easy.

Then, I was playing with the switch and found the cable test function - and yes it reported a problem with that one particular cable. What I was not expecting though was a comment that it was a specific distance from the switch. The switch actually has a Time Domain Reflectometer (TDR) built in but not mentioned in the documentation.

So, I now know where the problem is, but need to decide if I can locate the right cable in a bundle of 40 in trunking, under a floor and several metres from either end or do I live with it?

A cheap tone generator might be of help locating the cable.

Unless it's essential and relatively easy to get at, I'd be tempted to leave it.

Have had cables like that occasionally when testing stuff at work. In the couple of cables I've opened up I've found joints in the conductor from the manufacturing process which have failed.

I believed I needed two connection, so planned for four. As it turns out I need three (so far) of which two need to be Gigabit - so I am tempted to leave it, but if later on I need a fourth Gigabit I will be stuck as changing it then will be impossible. If the TDR is correct for position, I could get a junction box in but ... can I guarantee it!

I work with TDRs all the time and you cant take what they say as gospel, if they put you within 10M then thats great - but especially on an internal network I wouldn't expect it to pinpoint exactly where the break is, you may be able to change a section of the cable out but then if you're going to do that you may aswell change it end to end (or run addiotional and leave broken cable for phone / spare 100m). Unless you can see the damage I would work around it.

If changing it later will be impossible i'd be tempted to do this now.

Then, I was playing with the switch and found the cable test function - and yes it reported a problem with that one particular cable. What I was not expecting though was a comment that it was a specific distance from the switch. The switch actually has a Time Domain Reflectometer (TDR) built in but not mentioned in the documentation.

what switch are you using? - I might get one to add to my toolkit... though I know some laptops also offer a cable test function.

So, I now know where the problem is, but need to decide if I can locate the right cable in a bundle of 40 in trunking, under a floor and several metres from either end or do I live with it?

I would label both ends of the cable before going any further, then live with it for the moment - unless about to install carpet or something which would further restrict access

It's a Cisco SRW2024

I have tried it from both ends and with different length patch leads. Allowing for everything it seems to put the failure point in much teh same spot each time ...

the cable will probably stay - if I have space I pay run an additional though, just in case.

It's the kind of thing I would do now. It will be relatively easy to pull a new cable through, as you have the old one to use as a drawcord.

Might as well do it now while you're crawling about anyway.

In reply to a post by shtu:

It will be relatively easy to pull a new cable through, as you have the old one to use as a drawcord.

I think that'd depend on how many and the angle of any bends in the cable as well as diameter of any conduit and possible snagging with the other cables running through the same conduit.

It's a fairly straight run - 7 metres down a wall and then under the floor - but that is through various noggins and the underfloor heating pipes are there too! It sounds easy - but I know it will be a pain - the break is possibly halfway down the wall at a point where I have access ...

Can you get junction boxes rated at Gb? Any I've seen before weren't rated that high, though I've not often looked...

Apparently, yes. They are the ones with Krone terminals capable of taking two wires rather than two strips of terminals and a small PCB. If I do that and it fails, I will still have 100Mb.