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Don't make your own patch cables.

True story:

My first job out of college we made our own patch cables. Usually we'd make them "on demand" as needed for a new server or workstation. My (then) boss didn't want to buy patch cables even though we knew that we weren't doing a perfect job (we were software people, eh?). Any time we had a flaky server problem it would turn out to be the cable... usually one made by my (then) boss. When he left the company the first policy change we made was to start buying pre-made cables.

That was during the days of Category 3 cables. You can make a Category 3 cable by hand without much skill. With Category 5 and 6 the tolerances are so tight that just unwinding a pair too far (for example, to make it easier to crimp) will result in enough interference that you'll see errors. It isn't just "having the right tools". An Ohm Meter isn't the right testing tool. You need to do a series of tests that are well beyond simple electrical connectivity.

That's why it is so important to make sure the cables are certified. It isn't enough to use the right parts, you need to test it to verify that it will really work. There are people that will install cable in your walls and not do certification. Some will tell you they certified it but they really just plug a computer at each end; that's not good enough. I found the best way to know the certification was really done is have them produce a book of printouts, one from each cable analysis. Put it in the contract: No book, no payment. (and as a fun trick... the next time you do have a flaky network connection, check the book and often you'll find it just barely passed. You might not know how to read the graph, but you'll see the line dip closer to the "pass" line than on the other graphs.)

If your boss isn't convinced, do the math. Calculate how much you are paid in 10 minutes and compare that to the price of the pre-made cable.

Posted by Tom Limoncelli in Technical Tips


The cost thing works out in your advantage though if you have student workers who are getting paid (at the time) about $6.50/hr. It took me at most 5 minutes to make a category 5 cable that would pass with flying colors. Of course we also had a very good test set. Even still I think eventually we started buying 6 ft. patch cables because it wasn't worth the effort. For longer custom runs it was well worth it to use bulk cable.

I'm also proud to say that when we re-wired the entire 8 story computer science building with category 5 every single outlet was tested in full. Again though, cheap labor :-)

Thanks for posting this, Tom. This seems to be an issue that has more to do with pride or superiority than actual technical reasoning. Someone who makes their own cables is *clearly* superior in their technical skills than someone who buys them.

This kind of prejudice exists in many areas of sysadmin, and is usually justified by dubious logic.

Don't forget that the cost to buy cables is often cheaper than the time it takes to make and test them. This is a business aspect that technical people often forget.

I think most sysadmins should know how to make a patch cable, and they should have made at least a few in their lifetimes, just to understand what goes into it, and get a sense of the physical layer they otherwise would not have. (I guess they should also splice fiber but that's much more specialized.)

Having said that, not only should you not do it routinely with 15-foot cables available for under $2, but you also shouldn't treat cables as a precious commodity. Keep an inventory of cables and if someone loses one, just give them a new one. It's not worth the money in staff time to try and keep track of them. If a cable is at all misbehaving, a tab breaks, or the strain relief boots crack, recycle it.

I've been down this road, except I was a rookie AND the sysadmin in charge (the company was young). "lets make our own cat5 w/ the extra spool from the guys who wired up our office. Also lets use these sub par crimping tools. Also, what's 568b? Just make sure they're the same on both ends."

Over the next 5 years, almost every cable we made had to be replaced by hand. I think we had 2 out of 10 that were still good when I found it and replaced in anticipation of it's eventual failure.

HAHA! My first job involved a lot of making patch cables, but I was a part-time student employee making $7/hour, and we had Fluke meters to test the cables we were sometimes running under the floor across the machine room for the supercomputers so it made its own sort of sense. :)

Though many of the cables were station cables to connect to CAT3 premise wiring. SPECIALTY cables to map the premise USOC to TIA-568A, and we had special splitters so that one jack with four pairs could still serve two workstations, with some custom-made two-headed cables running from the patch panel to the network hubs.

I am glad to have "graduated" beyond making my own cables, but the advise to require signal tests from the contractor is gem. Thanks!


I'm on the fence on this subject... I've been making cables and using pre-terminated ones for almost 20 years. Many times, I find that I can get a neater job by custom making my patches since some cables in a rack need to go farther than others and I need to find creative ways to clean up the slack. I've heard lots of FUD over this over the years and tried to budget for some Fluke testers last year (got bumped) but, when the Fluke rep was out demoing the testers I pulled out a bunch of cables I'd made just to see how they measured up... thankfully, no problems! I think that any good system admin should be able to make a decent cable but that doesn't mean I think they are any better than someone who can't. The big thing I don't like is sloppy cabling, it looks like crap and is difficult to work on a cabling job that wasn't originally done well - I especially hate it when I've done a nice rack and someone comes in after and just hangs some cable or ties crazy knots in it in a feeble attempt to "make it neat".

When it comes to basic common sense in the system administration world it just makes me cry and wet my pants when a supervisor/boss/whatever can't get it.

For instance, when the whole world has come to accept that some kind of configuration management is needed and your boss insists that "it's just too hard, let's do it our way (for loops)"... I seriously consider if I'm in the right job.