So, a few weekends ago, I got a 1000 ft spool of Cat6A cable, some Cat6A keystone jacks, some 25 ft metal fish tape, and some other miscellaneous items for an in-wall Gigabit Ethernet home cabling project. Cool! Alas, being a first timer at this kind of thing, there were some errors made the first time through and some lessons to be learned. So, here is my summary of what those lessons are.
- Use T568B wiring scheme, period. Don’t bother even considering T568A. If you look around at the color coding in all the Ethernet patch cables you have, you’ll notice they’re all T568B. Besides, Internet HOWTOs on building your own patch cable don’t bother even mentioning T568A wiring, they only specify a single wiring scheme, and that one matches the color codes for T568B. Also, chances are that if you look carefully at the hints in the cabling, jacks, and equipment you’ve bought, it’s all optimized to make T568B wiring physically the easiest to wire up. Not to mention that the Ethernet cable companies simply sell much more T568B equipment than they do T568A.
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If there is a question you have about some technical information, don’t be fooled by the Wikipedia article on the subject, it is written with an inherent bias in “official” writings rather than common knowledge. Instead, search around on the Internet with a priority toward Internet discussion forums. There is where you will find the real knowledge from real community members.
This is specifically the problem I’ve made: I was unsure whether to use T568A or T568B wiring, so I went to Wikipedia for guidance. Wikipedia made it sound like T568A was better, so I went with that. Bad idea… it may have seemed like a better idea in the 1990s, but the only reason why was for the sake of color compatibility with old analog telephone lines. Analog telephone lines? Ha! Even my older family relatives who were out and about using land line telephones at the time have practically long since forgotten that analog telephone lines were even a thing. I mean, seriously. If they ever want to call someone in the modern era, their smartphone is their first go-to device. The heck with analog telephone wiring codes! Who needs to bother requesting a second telephone line to their apartment, house, or bedroom in 2019?
With this base of common consumer electronics knowledge, there is absolutely no reason to believe that the next generation of techies will even lift a finger toward considering wiring schemes compatible with analog telephones. Please, please, please, just use the same color wiring scheme you see in your mass market manufactured computer Ethernet cables. Yes, the thing that you bring to a new wireless access point when someone requests more smartphone and tablet Internet usage capabilities.
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Do not plug in an RJ11 6P6C analog telephone plug to an RJ45 8P8C Ethernet jack. Why not? Well, as the RJ11 plug is only designed for 6 positions, the edges of the RJ11 plug have raised outer edges that will press up against the outer two contacts on your 8P8C Ethernet jack. Once you remove your RJ11 plug, you may realize that the outer two contacts in your Ethernet wall jack were ever so slightly bend upward. Sure, you may still be able to get your computers to connect okay, but I can’t help but point out the damage you’ve done to your shiny new jack after the very first foolish insertion done with an analog telephone jack. So, that means there is no such thing as straight backwards compatibility with telephone plugs. Please, please, please, if you so dare to be using an analog telephone over the Ethernet wiring, build a converter cable proper with an RJ45 plug on one end and a RJ11 jack on the other, and plug your old fashioned analog telephone into that RJ11 jack.
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If you crimp your own Ethernet patch cables, please note that the contacts on uncrimped plug heads are raised up. Do not plug one of these plug heads into any jack, or you risk damaging the jack by bending the contacts upward! When you crimp the Ethernet heads onto the cables, please make sure you push the contacts all the way down so that they are sunken beneath the plastic ridges, otherwise you risk damaging your jacks by inserting such plugs. In practice, I’ve found that this means you can’t do the clever minimal tools crimping technique of using a screwdriver to push down the raised contacts because I was unable to push them down with enough force to get them below the threshold. Nope, you gotta have the real crimping tool.
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How do you test your Ethernet cables with punch-down block Ethernet jacks installed, using only cheap, easily available home equipment? Computers and switches, period. Do not bother with electrical continuity testing to verify all connections are wired, it is a joke. Only do this if you are desperately curious to learn what is going on. But, seriously, don’t bother. The tools you use to test and diagnose RS-232 serial cable wiring connections won’t remotely stand a chance to giving you insight as to why an Ethernet cable isn’t working. I mean, come on! Seriously, if you’ve been following along my previous blog posts, I’ve noted just how remarkably slow “fast” 56 kbps serial communications is compared to “slow” 10 Mbps Ethernet.
At Ethernet communication speeds, mere electrical continuity doesn’t determine whether a cable is game-ready or not. With high frequency signals, sharp edges, nicks, fractures, and other deformities that deviate from smooth cable geometry with clean-cut ends and punch-down termination cause high-frequency signal reflections off of the deformities such that the signal interferes with itself, thereby greatly reducing the speed classification of the cable by a factor of 10, 100, 1000, or even more.
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Be careful about jacket stripping. If you have the Ethernet jacket stripper tool, great. However, if you’re attempting to get by with less tools and are using a pair of scissors instead, then use that pull string to strip back more jacket, and cut off all the wires clean where you were using the scissors to weaken and tear off the jacket. That way, if you happened to nick any of the wires, you would have cut off the nicked part of the wire cleanly after trimming.
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If you wire an Ethernet cable to a punch-down block Ethernet jack, and it doesn’t work, do a clean cut through the whole cable and try again. If you have punch-down blocks on two ends and are unsure of which one is the bad one? Cut off the one you did first. Chances are you knew more of what you were doing on the second one, and it could just as well be good and usable.
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If you’re bringing down spread-out wires in a punch-down block, and it doesn’t quite work right, try to avoid coming back up. If you do have to come back up, you might as well cut all the spread-out wires and try again cleanly. Otherwise, you could get the aforementioned fracture signal interference problems.