# 4 wire Cat 5/6 for internet? Please help!!



## Tony Vee (Apr 6, 2013)

I am currently troubleshooting a problem one of my customers has where he told me he lost internet access on one of his desktops. Now I am an electrician who usually works in the commercial field so I can say I don’t really have much experience in the data field as a whole and was hoping that someone who’s in the field who knows what they’re talking about can help me please?!? 
When I checked his cat 5/6 wiring he has the typical RJ-45 jacks but I noticed that where his computer is plugged into the RJ-45 jack he only has 4 of the 8 conductors from the cat 5 line landed on the plug. The other 4 conductors are routed to an RJ-11 jack that I’m assuming are his phone lines. Can anyone please explain this to me because I thought you need all four pairs to establish an internet connection through the cat5/6 line. Please help any information would be greatly appreciated. 


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## CoolWill (Jan 5, 2019)

10 megabit and 100 megabit protocol only uses 4 wires.


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## LGLS (Nov 10, 2007)

You don't need to know a thing about data to troubleshoot this. It worked before. 4 wires didn't magically yank themselves off a connector and land themselves onto a phone jack.


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## MikeFL (Apr 16, 2016)

Plug in a laptop at the same place and see if it gets on line.


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## Jerome208 (May 10, 2013)

The old traditional Cat5 only used 2 of the 4 pairs for the data. One pair one direction and one pair the other direction (TxD/RxD). The other two pairs are just idle and don't do anything.


They are occasionally stripped out and put to use for another data drop, or voice signals.


There is some debate on whether this "meets spec" but it has worked for me.


As the others have stated, not likely the source of your problems. But sloppy wiring practices in order to accomplish it might be.


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## 99cents (Aug 20, 2012)

I make sure he has power. Beyond that, he can hire a propellorhead.

Of course, I don’t even know how to operate a TV remote. My kids change the clock on my car radio.


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## sparkiez (Aug 1, 2015)

99cents said:


> I make sure he has power. Beyond that, he can hire a propellorhead.
> 
> Of course, I don’t even know how to operate a TV remote. My kids change the clock on my car radio.


We call that a 12:00 flasher :vs_laugh:







troubleshooting data can be nuanced. The basic steps are:

1. Check the cable. Try another device and see if you get a connection
2. Check layer 2/3 (start-->run-->cmd and ping the default gateway)
3. Start checking for firewall/driver issues


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## Tonedeaf (Nov 26, 2012)

if some asshole only jacked out 4 of the 8 wires.....it prolly isn't a good connection.

https://www.homedepot.com/p/Klein-Tools-VDV-Scout-Pro-2-Tester-Kit-VDV501-823R/205209866

get that tester and test it.


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## splatz (May 23, 2015)

I think the OP is probably gone but this was a common practice at one time. The 10 and 100 mbit ethernet run on pins 1, 2, 3, and 6; most phones run on a single pair, the blue pair, landed on the center pins, so 4 & 5 of an 8-pin jack. This was never considered a great practice but it pretty much works. 



It sounds like maybe he had crimped up a jackwad splitter cable between the computer / phone and the wall, which probably failed when someone tugged on it or looked at too hard.


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## Stuff (Oct 14, 2012)

A few years ago ran into an issue at a site that was using only two pair for some drops - cable was split so two pairs went to another jack. Things worked until they did an equipment upgrade. I don't remember for sure but think it was from one brand gig switch to another. The new one tried to negotiate 1000mb/s and kept on failing. Hard coded ports to 100mb/s until able to pull new cables.


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