RJ45 Connectors

Summary

RJ45 connectors are used for 10-baseT and 100-baseT. This document includes the pinouts of these connectors.

This page was created as there were a lot of questions about making RJ45 connectors and RJ45 null-modem connectors. The source of most of the information herein was from a series of E-MAILS on the redhat list.

Overview

The RJ45 connector is a telco-like connector used for networking. This is used for 10-baseT, 100-baseT, and token ring. There are two formats, TIA/EIA T568A (DOE) and TIA/EIA T568B.

http://www.k12.hi.us/~tethree/96-97/course2/RJ45diagram.html

You probably want to use TIA/EIA 568B, which simplifies things with telco patch panels.

Then if you have a cable with one 568A end (obvious if you look at them) you automatically know it's a crossover cable. (One end 568B and one end 568A equals crossover.)

For reference, print that page out on a color printer and put it up on the wall. Besides being a good reference, it makes a nifty poster. :-) (I'm thinking of finding somebody with an 11" x 17" color printer for mine.)

568B

Assuming you're looking at the side of the connector WITHOUT the little tab, 568B wiring is:


    white-orange
    orange
    white-green
    blue
    white-blue
    green
    white-brown
    brown

    w.....b  [tab DOWN]
    h     r
    /     o
    o     w
    r     n
      xxx
      xxx
      wire

Only 4 wires matter for Ethernet (the orange and green pairs) but you should always wire it properly anyway.

The wires that matter for token ring, BTW, are the green and blue pairs.

It's always ticked me off that it isn't the blue and brown, because then an Ethernet crossover cable would work as a normal token ring cable, but as it stands an Ethernet crossover just doesn't do anything with token ring. You can't crossover token ring. :-(

568A

For 568A, you just swap the orange and green. Thus:

 

    white-green
    green
    white-orange
    blue
    white-blue
    orange
    white-brown
    brown

    w.....b  [tab DOWN]
    h     r
    /     o
    g     w
    r     n
      xxx
      xxx
      wire

Crossover Cable

As I said, if you make one side 568B and one side 568A, you have a crossover cable.

Notes

Invest in a GOOD crimper. It's worth the extra money in terms of aggravation and troubleshooting time. A good tester is also very useful and highly recommended.

A lot of diagrams and instructions look at it from the side WITH the tab. So if you're making a cable, pay attention to which way the directions you're using run! In fact, that URL I refer you to above shows it from the tab side. Pick one way, and always do it that way. If you do, in no time at all you'll have this memorized, trust me.

Be sure to buy some extra connectors and leave your wires a bit long as it is very easy to mess up when first making cables. A very common mistake is to make the cable upside down (e.g., use a diagram for TAB up but make the cable with the TAB down -- oops).

Oh, some instructions will say "white-orange and orange-white" and so on for all the wires. "white-orange" is obvious, it's a white wire with a thin orange stripe around it. "orange-white" is an orange wire with a thin white stripe. It's so thin, you often can't see there's any white at all. And some wire doesn't have the white stripes at all. Just remember that the first word is the important one, if confronted with one of these confusing sets of documentation.

Original mail header info:

 Subject: Re: Totally off topic: RJ45 fab
   Date:  Tue, 5 May 1998 11:00:46 -0500
   From:  "Shawn McMahon" <smcmahon@chickasaw.com>
     To:  "Rob Goodwin" <goodrob@shaw.wave.ca>
     CC:  "Redhat List" <redhat-list@redhat.com>

For comments, suggestions, or corrections: whampton@staffnet.com