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I'm rewiring a rack, and would like to have the cabling cut to length to make things as tidy as possible. The suppliers of Cat5e/Cat6 cable I've found only really supply bulk cable in multiples of 100m. I don't need anywhere near that sort of quantity, and buying that much of each colour required would be unnecessarily expensive. As yet, I haven't found many suppliers that would supply bulk cable in smaller lengths for what I need.

My question is this - If I want to be able to do the above, should I be:

a) Continuing to look for a supplier that will supply shorter lengths of bulk cable more suited to my requirements (perhaps cut to order?). Is this common?

b) Buying individual pre-made patch cables, cutting them to length and crimping a new connector?

c) Give up on the idea and just use the most suitable length of pre-made patch cable?

d) Some other option that I haven't considered?

I should also mention that I'm aware of the labour cost argument regarding making your own cables vs. buying pre-made ones. I certainly wouldn't be doing it for every cable I use, but for cabling up a rack, I think the extra tidy-ness acheived is worth while.

Any advice greatly appreciated.

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Newt, I'm aware that you can't accept answers to all your previous questions, but looking at them I think you could do a bit better than 25%. May I encourage you to do so? – MadHatter Apr 27 '12 at 8:43
You're quite right. Done. – dbr Apr 27 '12 at 8:52
Thank you! The question-answer thing is what makes SF work. – MadHatter Apr 27 '12 at 9:51
up vote 5 down vote accepted

I would say that what you're looking for is very uncommon. People who do this sort of thing for a living (data cablers) would go through hundreds of feet of cable a week, in all the colours of the rainbow, and so buying by the giant spool is no problem for them. People who don't do this for a living typically aren't good enough to do a couple of hundred crimps reliably and quickly enough to make it worthwhile.

I buy cables pre-made in the appropriate lengths needed, then just take up the small amount of remaining slack in neatly cable-tied "zigzag" routing on the side of the rack. Does the job nicely, you just need to invest in massive numbers of cable ties.

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+1. A great way of getting rid of that excess slack is demonstrated here:… – Mark Henderson Apr 27 '12 at 9:34
@MarkHenderson: I think that's the image that motivated me to start doing that. Thanks. – womble Apr 27 '12 at 9:38
+1 My first time crimping cables was my last time crimping cables. Out of 80, half were bad. Definitely not my strong suit. – squillman Apr 27 '12 at 10:27
Don't use so many cable ties; get a roll or two of single velcro tape (back sticks to front) – mpez0 Apr 27 '12 at 12:21
Don't make custom cables. Your time is better spent. I remember traveling to South Africa in 1993 to install a network. I was expected to make my own cables and promptly blew through all the connectors with not one good cable to show. Fortunately, we found RJ45 connectors locally and I got better at it. – uSlackr Apr 27 '12 at 12:26

Having made up far more cables than I care to think about I'm going to suggest option C as your best bet. I personally would make up my own cables and have done so before but I can assure you that when you're talking about a rack worth of cables it really is a tedious job at the very best of times and downright torture for anyone not well experienced at it.

The fact that you're asking the question at all hints to me that you haven't made up a great many cables yourself, as you appear to be unaware of the amount of work involved. Figure a cable per minute at the start (if you are quick at it) and a cable every couple of minutes after the first hundred or so, because you slow down when the fingers get tired and cramped. To do the job well every cable also needs to be properly tested, which will take say another half a minute or more. Now figure out how much time that's going to take you for the whole job, at the end of which you'll almost certainly be cursing your decision to take that route.

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Go option C, unless you have the equipment and experience to crimp and test properly.

I have worked in IT for a long while now and it is a long time since I even bothered thinking about this. I have better things to be doing than saving a buck or two on cables. Your time spent doing any job is worth $80-$120 per hour to most businesses. When you factor that in it makes more sense to purchase ready made cables that are consistent and generally look nicer as well, and use the time saved to be more productive with other things.

If you want to be a data cabler be a cabler. It is a profession in its own right and something I don't do as a system administrator.

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Being able to make your own cables and go both ways with male or female ends has a certain je ne sais quoi craftsmanship quality that may come in handy during a system administrator's data center zombie apocalypse.

Beginner's luck using "Ghetto/Hillbilly" trial and error with a 110-punch down tool and puck usually works for Cat 5 at 100 Mbps and Cat 5E for 1 Gbps. A few things can go wrong punching down jacks (why a male name for a female device?) and crimping plugs. Mis-wires and an IDC coming loose are common and relatively easy to identify with a verification test device costing less than $100.

Even if you make your own cables you still should leave a 6 to 12 foot service loop of cable in the ceiling (if a drop ceiling) or under the floor (if using raised flooring) for inevitable changes in the MDF/IDF/Telecomm Room rack and a service loop for the wallplate/jack user's end too. A cable an inch too short incurs the cost of running 2-cables. Buying pre-made cable may mean you just have bigger or smaller service loops.

Zig-zagging in the rack cable management areas can fill the volume up and be messy if you have too many zigs and zags.

Testing is done at 3-levels: Verification, Qualification and Certification

Certification includes:

  • Wiremap
  • DC Loop Resistance
  • Propagation Delay
  • Delay Skew
  • Cable Length
  • Insertion Loss
  • Return Loss
  • Near-End Crosstalk (NEXT)
  • Power Sum NEXT (PSNEXT)
  • The Equal-Level Far-End Crosstalk (ELFEXT)
  • Attenuation-to-Crosstalk ratio (ACR)
  • Power Sum ACR (PSACR)

If you're wiring Cat6 or 6A for 10 Gbps you probably should hire a professional that owns a Fluke DTX-1800 and DSX-5000; IDEAL Industries LANTEK; JDSU Acterna Certifier40G; or Agilent Wirescope Cable Analyzer

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I think that crimping your own cables isn't a good idea. It is labor intensive, with few benefits and for n cables you create n*2 possible points of failure when doing this yourself if you haven't any good testing equipment. Also, shopping around will offer you a wide variety of pre-made cable lengths. In the past, I got cables measuring 30, 50, 100, 150, 200 cm, which should be sufficient to get a tidy rack.

Also, if at some point in the future, you will have to rearrange the rack for whatever reason, you are going to do all this over again.

So, my answer is option c.

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