Ethernet/rj45 wiring

[star_weaver]

Does the order matter or does the order not matter along as the wire strands are the same on both ends? 

[Eigenvektor]

https://www.iplocation.net/rj45-wiring

There's straight-through and cross-over⁽¹⁾. Modern network cards have auto-sensing so in general you can use either cable now. In the past you have to use straight to go to a router and cross-over for PC-to-PC connections.

 

1) Technically there's also some proprietary stuff like roll-over required to e.g. connect to Cisco terminals and the like, but those are uncommon and only for specific devices

[Ralfi]

For ‘straight’ cables, it doesn’t matter.

 

If you know you’ll be doing many of them, it’s good to follow the official colour code though, so it becomes a habit.

[AbydosOne]

43 minutes ago, Ralfi said:

For ‘straight’ cables, it doesn’t matter.

 

If you know you’ll be doing many of them, it’s good to follow the official colour code though, so it becomes a habit.

It kinda matters, in that you should have each twisted pair of conductors correspond to a differential pair for best EMI noise rejection.

[Ralfi]

17 minutes ago, AbydosOne said:

It kinda matters, in that you should have each twisted pair of conductors correspond to a differential pair for best EMI noise rejection.

I took the OP as saying the wires will be in the same order at both ends & that they were asking if it matters which order they are in.

 

My response to that was that it doesn't matter what order the wires are in, so long as the order is the same of both ends of a straight cable.

 

If I misunderstood the OP, apologies.

[mariushm]

The order DOES matter. 

 

For a regular ethernet cable, use one of the two orders, and use same choice on both ends of the cable.  The recommended one and most commonly use is the B variant where you have the white-orange wire the first (if you look at the connectors with the contacts on top and clip on bottom).

So a regular cable has the wires in the same order on both ends. 

 

If you want to connect two computers together without using a switch, in the old days of 100 mbps network cards you had to use a crossover cable, which basically flips the transmit and receive pairs of wires on one connector. 

Modern network cards auto detect the wires and their role so you don't need to make a cross-over cable with modern network cards, but should you wish to nothing stops you.  For gigabit and higher speeds, you have to rearrange ALL FOUR pairs of wires, like in the picture below  (leave one connector normal, and the other like on the right side of the picture).   

 

 

 

100 mbps and older ethernet network cards did not have this auto detect feature and for those, you had to make a crossover cable.  But, because 100 mbps ethernet only uses 4 out of the 8 wires to transmit data, leaving the other four unused, you can make a simplified crossover cable, like in the picture below. 

 

So as you can see 1+2  is on pair (transmit data) and 3+6 is the receive pair. Because the other pairs 4+5 and 7+8 are unused, they can be left untwisted.  So again, this is ONLY for 100 mbps. If you use such crossover with gigabit cards, they'll probably keep trying to auto detect wire order and fail, because it's neither a straight cable and it's not all four pairs rearranged like in the picture above.  You would probably get it working by forcing the network card down to 100 mbps from Device Manager but then you lose speed.

 

 

 

 

For 10 mbps and 100 mbps, most likely you'll get away with using any pair as transmit pair  and receive pair .. for example use white-blue and blue for 1+2 (transmit), and white-brown and brown for 3+6 (receive)  ... in fact often people saved ethernet cable by installing two ethernet jacks or wall sockets at the end of one cable, and inserting only the 4 wires in the connector... the 2 100mbps signals go on their separate receive and transmit pairs so it all works OK. 

 

But with 1 gbps  all four pairs have to twisted properly in a cross over cable, or not twisted at all, leaving the network cards auto detect things.

[star_weaver]

5 hours ago, Ralfi said:

I took the OP as saying the wires will be in the same order at both ends & that they were asking if it matters which order they are in.

 

My response to that was that it doesn't matter what order the wires are in, so long as the order is the same of both ends of a straight cable.

 

If I misunderstood the OP, apologies.

Yeah, I just don't really want to have to twist wires over each other, makes it hard to keep them in the same order, was thinking of putting  the same color pair together/side by side instead of the official layout. Green next to green/white then blue-blue/white and so on

[Ralfi]

2 minutes ago, star_weaver said:

Yeah, I just don't really want to have to twist wires over each other, makes it hard to keep them in the same order, was thinking of putting  the same color pair together/side by side instead of the official layout. Green next to green/white then blue-blue/white and so on

Here's a tip - expose 50mm of wires, un-twist them as naturally as possible, arrange them in order & straighten them by running your fingers along them multiple times.

 

Then snip them to length, before feeding them into the plug.

[star_weaver]

Just now, Ralfi said:

Here's a tip - expose 50mm of wires, un-twist them as naturally as possible, arrange them in order & straighten them by running your fingers along them multiple times.

 

Then snip them to length, before feeding them into the plug.

Thats what I do but half the time I end up putting am orange where brown needs to go or I swap a solid with a white making it so I need to redo that end of the cable

[Ralfi]

11 minutes ago, star_weaver said:

Thats what I do but half the time I end up putting am orange where brown needs to go or I swap a solid with a white making it so I need to redo that end of the cable

What kind of plug are you using?

 

There are three that i'm aware of; CAT5, CAT6 & CAT6 with a sleeve, the latter of which are easiest to work with.

[star_weaver]

1 minute ago, Ralfi said:

What kind of plug are you using?

 

There are three that i'm aware of; CAT5, CAT6 & CAT6 with a sleeve, the latter of which are easiest to work with.

5

[mariushm]

The wires are colored like that for a reason.

Each two wires with same color (blue, orange, green, brown)  are twisted together and then insulated from the other pairs within the cable 

Each pair even has a different number of twists per feet/meter whatever, for extra protection against noise, picking up signals from the other pairs, whatever. 

 

Pins 1 and 2 must be wires from same color,  pins 3 and 6 must  be wires from same color,  then pins 4+5 should be wires from same color, and pins 7+8 should be wires from same color.  

 

Crimping ethernet jacks is fairly easy ... strip 1-2 inches of insulation, untwist about a  half an inch from each pair, use the blade to cut them to same length, insert the wires in the channels until you hit the back with all the wires, pull out and use blade again to shorten the wires and insert all again, push on the sleeve until the sleeve is after that bump that's gonna hold the sleeve once crimped ... done. 

On a properly made ethernet cable, the individual wires are not untwisted for more than around 1/3 inch,  around the width of your small finger on your hand.

[star_weaver]

3 minutes ago, mariushm said:

The wires are colored like that for a reason.

Each two wires with same color (blue, orange, green, brown)  are twisted together and then insulated from the other pairs within the cable 

Each pair even has a different number of twists per feet/meter whatever, for extra protection against noise, picking up signals from the other pairs, whatever. 

 

Pins 1 and 2 must be wires from same color,  pins 3 and 6 must  be wires from same color,  then pins 4+5 should be wires from same color, and pins 7+8 should be wires from same color.  

 

Crimping ethernet jacks is fairly easy ... strip 1-2 inches of insulation, untwist about a  half an inch from each pair, use the blade to cut them to same length, insert the wires in the channels until you hit the back with all the wires, pull out and use blade again to shorten the wires and insert all again, push on the sleeve until the sleeve is after that bump that's gonna hold the sleeve once crimped ... done. 

On a properly made ethernet cable, the individual wires are not untwisted for more than around 1/3 inch,  around the width of your small finger on your hand.

I know how to do it, it's just a bit hard to line colors up properly for me

[Lurick]

I would get the passthrough RJ45 plug ends so you can feed extra wire through the end of the cable, it makes life SO much easier

[Needfuldoer]

12 minutes ago, Lurick said:

I would get the passthrough RJ45 plug ends so you can feed extra wire through the end of the cable, it makes life SO much easier

As long as your crimper has a sharp guillotine blade on it, yes.

 

If the blade is dull, and mushrooming the cut ends so they just about touch, that can make some problems that are fun to track down.