A friend of mine recently posted this image of a hideous network-cable tangle:
I have invented an algorithm for fixing this kind of mess. Probably other people have developed the same technique before, but it wasn’t taught to me and I’ve never seen it written down. Here it is…
First, start by assembling your equipment. You will need a labeling gun (the kind that can put lettering on a short length of sticky-backed plastic tape), a bunch of cable ties (a couple dozen for this mess), a pad of paper (ideally, blue-lined graph paper), a clipboard, and a pencil. Finally, a bunch of patch cables in 12-inch and 6-inch lengths.
For some jobs, like this one, you’ll want a nice sturdy stepladder, something you can use to put the bulk of the cable tangle at or below shoulder height. If you need to reach above shoulder height to get at the connectors, the job is going to fatigue you faster than you realize – and that can easily lead to mistakes that are quite difficult to recover from. Hard work is not a virtue here; make the job easy on yourself so you’ll get it right.
The tangle pictured is about a three-hour job using this method, maybe four; scale appropriately for your mess . Allocate time so you can do it all in one go, otherwise you may have trouble fully recovering intermediate state.
Your first step (and the longest part of the job) is the crucial one. Trace each individual cable through the mess without removing it. Now label both ends of the cable, right near each connector, with a unique code. Same code for both ends.
Second step: Make a sketch of the patch panels. The reason graph paper helps is that usually the equipment racks will be laid out so the cable connectors fit on a rectangular grid. Sketch in each connector as a little box, and each rack unit as a surrounding frame. Leave enough room in the boxes to write inside; if there are unused connectors on the units, X them out in your diagram. When you are done, your sketch should resemble a crude plan of the racks.
Third step: Pick a cable. Note the code at one end in the corresponding box on your sketch. Unplug that end. Work the cable end through the rest of the mess until it is fully untangled and you can see the entire length. Identify the end still attached and add its code to your sketch. Unplug the other end and lay the cable aside. Repeat this procedure until all cables are removed. If you can recruit someone to help you, the single most useful thing that person can do is eyeball-check each code pair on your diagram as you pencil it in.
Step Four: At the end of this step, you should have a filled-in diagram that will tell you exactly how to rebuild your patch network. Do that. But this time, you’re going to do three things differently. First, you’re going to use shorty cables wherever you can to avoid hanging loops that can get tangled. Second, you’re going to use cable ties to bundle together parallel runs.
Thirdly, and most importantly, each new cable gets a label at both ends. Once you’ve done this, your patch network will no longer be a nightmare to manage. And the next poor sod who has to cope with it (quite possibly yourself in six months) will bless your foresight.