10Base-T question

[ablang]

To make a 10Base-T crossover cable, which wires would you cross between the connectors?

a. 1 with 2; 3 with 4
b. 1 with 3; 2 with 4
c. 1 with 3; 2 with 6
d. 1 with 2; 3 with 6

[wvulf]

To make a crossover cable for a 10BT (using unshielded twisted pair):

You need to simply remeber this:

Pin one is always the left most pin, as you are looking down at the plug (With the locking tab on the other side that you can't see ) that goes into jack of the wall. (Hope you understood that run on senetence... ). Pin 8 is the right most.

There are eight wires in UTP, but only four of them are active. These are the wires that go to pins 1, 2, 3, & 6.

The normal order of Tx/Rx pairs is Pins 1 & 2, and Pins 3 & 6. The crossover is between these two sets. Pin 1 crosses over and becomes Pin 3, and Pin 2 crosses over and becomes Pin 6. The same thing happens with the second set of pins (3 & 6), and they become Pins 1 and 2. When in doubt, just multiply or divide by three. If you multiply Pin 1 x 3, that means it will become pin 3. Pin 2 x 3 means that it will be pin 6. Divide by 3 for Pins 3 & 6.

That should help, but if you follow the standard color codeing that most networks use (others may have different orders for their colors), Pins 1 and 2 will use the same pair color of wires and so will pins 3 and 6.

The normal color order that we use where I work is:

Pin 1 Orange-White
Pin 2 Orange
Pin 3 Green-White
Pin 4 Blue
Pin 5 Blue-White
Pin 6 Green
Pin 7 Brown-White
Pin 8 Brown

Normally, both ends would be the same, but for the crossover end of your crossover cable, it would become:

Pin 1 Green-White
Pin 2 Green
Pin 3 Orange-White
Pin 4 Blue
Pin 5 Blue-White
Pin 6 Orange
Pin 7 Brown-White
Pin 8 Brown

This was a little long, but should give you a complete understanding of setting up a TCP/IP network using both standard/and crossover cables...

Good luck

Wvulf

[ablang]

Thanks for the response. So I think your answer would be... C.

That makes sense to me now.

[ablang]

Correct! It's C. 10Base-T can use Category 3 wiring, which has four wires.

[BobD]

wvulf is absolutely correct. And here are a couple of things you should keep in mind:

1. 10BaseT only requires 4 wires to function: 1, 2, 3 & 6 (2 pair). But as most of us are using Cat5 which has 4 pair, you should connect all 4 pair - makes 'em feel useful and decreases cross-talk.

2. When you look at all 8 wires in a RJ45 plug, you'll notice that the color arrangement will always be white-color/color, white-color/color. Even when making a crossed-pair cable.

3. The color coding is an international spec that has two versions: TIA/EIA-568A and 568B. The common spec in this country is 568B, while the rest of the world tends to use the A version. Go figure.
ps-Cisco includes a patch cable with their devices - they use the A version.

4. Here's how the colors change from one end to the other:

Plug1 Color Plug2
------------------------------
Pin 1 W/Orange Pin 3
Pin 2 Orange Pin 6
Pin 3 W/Green Pin 1
Pin 6 Green Pin 2

All other pairs remain the same.