Introduction: Crossover Dongle

Picture of Crossover Dongle

If you're like me you've got a bah-jillion cables floating around in your computer bag. I got tired of having to have two separate types of cat-5 cables, straight and crossover, so I came up with this little gadget that will turn any straight cable into a crossover cable.

Step 1: Parts

Picture of Parts

Here's all the tools/parts you will need:

1 x RJ45 Crimp Tool
1 x Push Down Tool (some keystone jacks come with their own)
1 x Wire Strippers
1 x Cat-5 Cable
1 x Cat-5 End
1 x Keystone Jack
1 x Hand with at least one finger and opposable thumb

Step 2: Prepare the Cable

Picture of Prepare the Cable

Strip back the outer insulation on one end of the cable, so you've got about 1.5" of wire to work with. This will be the "male" end of the cable.

Untwist each of the four pairs and arrange them as follows:

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

This follows the 568B wiring schema which is what I always use when wiring up patch cable. To make normal 10/100 base crossover cable one end needs to be wired 568B and the other end needs to be 568A. Basically what you are doing is swapping the orange and green pairs from one end of the cable to the other, hence the term crossover.

**Note that for gigabit ethernet you will need to cross the blue and brown pairs as well.

Trim back the excess wire, give your self about .5" to .75" to insert into the Cat-5 plug.

Step 3: Crimp

Picture of Crimp

Insert the wires into the cat-5 plug. Make sure that the "notch" side of the plug is facing down as you slide the wires in. Otherwise, you'll have created your own unique wiring scheme, which is cool, but no other existing devices will understand it.

Once the wires are in the plug, insert the whole <william-hung-voice> she-bang </william-hung-voice> into your crimp tool.

If you're smart you bought a ratcheting model. If you're a cheap bastard like me (ex g/f's words, not mine), then your's doesn't ratchet either, and you'll need to squeeze down and hold for a good ten seconds.

Step 4: Wire the Keystone Jack

Picture of Wire the Keystone Jack

Your keystone jack should have some sort of legend that will show you how to wire it up. To wire this jack 568A I had to wire:

Green / White to pin 1
Green to pin 2
Orange / White to pin 3
Blue to pin 4
Blue / White to pin 5
Orange to pin 6
Brown / White to pin 7
Brown to pin 8

Wait a minute, that's exactly how the diagram shows 568A is wired! What a strange coincidence...

**Again, in order to utilize gigabit transfer rates you will need to swap the blue and brown pairs, so instead of the above it would be: Brown / White to pin 4, Brown to pin 5, Blue to pin 7, and Blue / White to pin 8.

If you've got a shop that you can pilfer other people's tools from, then go steal... err, borrow a nice push down tool, which cuts the wire for you automatically.

Some keystone jacks come with their own tool, but it doesn't cut the wire for you. For that you'll need a pair of diagonal cutters, or just use a knife.

Step 5: Done

Picture of Done

Put the cover on the jack. Poof, you're done. Now you can network two PCs sans a hub or switch.


MorganGardiner (author)2014-01-15

Very handy.

Pasit (author)2007-08-22

i wasnt trying to be critical it was supposed to be a question?? and wtf's the difference between a stait cat5 cable and a crossover cable, and whats a cat 5 cable?

srmousse (author)Pasit2007-11-06

cat 5 cable is the proper term for the most commonly used network cable (the thing that plugs from your internet router to your computer... similar to a phone cord but with more pins). The purpose of a crossover cable is to eliminate the need for a network hub (a device used to network several computers together) when connecting two computers together (or even xbox's for that matter). Basically the crossover cable crosses 4 of the wires so that the two computers (xbox's) can talk to each other.

Klaudiuszm (author)srmousse2012-03-10

I just wish to clarify here "the thing that plugs from your internet router to your computer... similar to a phone cord but with more pins" that refers to all Ethernet cable not just cat 5. And the cables work by having computer 1's output go into computer 2's input and vice versa. And Pasit, Cat5 is a standard of cabling, rated at 100Mbps and 100 meters, being theoretical.

rahulait (author)Pasit2010-02-28

to be more precise, a cat5 cable is having 5 twists per 1 inch of the cable. its a standard... similar to this we have cat3 cables, cat4,cat6 cables....

festec (author)2011-12-26

that type of cross cable over has been around for years ! if you need one for giga bit then you cross over the blue and the brown pair... I have been making them for years. here is a picture of one in the internet archives back in 2001
you might have to cut and paste the link

GitarGr8 (author)festec2012-01-05

Yep, I wasn't claiming to have invented this, just wanted to show people how to make them. :)

festec (author)GitarGr82012-01-15

Jay Stapleton in Thunder Bay phoned me back in 1999 asked if I could make him one ....I think he is the first to come up with that type of cross over cable !
Way to go Jay

Mojo_JoJo (author)2011-06-03

I made mine like this, it accepts two straight cables and crosses them. I find this easier to carry in a laptop bag. It originally had two female connectors connected in stright through configuration, it was pretty easy to open and cross the pins of the socket. HTH

maxstevenson (author)2009-05-18

of course! so logical... this should be a standard tool. Is your name Spock, by chance?

GitarGr8 (author)maxstevenson2009-05-18

Ha, sorry to disappoint, but it's not my name. Plus, I think this is something Scotty would have come up with.

hintss (author)GitarGr82010-07-20

or the doctor or Data or teh interwebz

va1cho (author)2010-04-19

I think this tool is better choice because you need to do nothing and price is cheap.

GitarGr8 (author)va1cho2010-04-19

Actually I like this one the best, but then if you just buy something, you miss out on the enjoyment and experience of building something yourself.

Redgerr (author)GitarGr82010-07-08

i agree with you GitarGr8, the thinkgeek one is superior however that takes all the fun out of it.. buying stuff isnt allways the best way!

DraakUSA (author)2009-11-19

With newer equipment you almost never need this, since most new equipment will auto-detect.  However, this is handy to have for equipment that doesn't.  I've had one in my toolbox for several years that I use when I need it.

Pasit (author)2007-08-22

i dont get the point of this instructable, u just turned one "outy" end into and "inny" end. so the "outy" end of the other cable that would be plugging into the orange "inny", couldnt it just go strait into the port on the computer istead of through that thing??

GitarGr8 (author)Pasit2007-08-22

Do you know the difference between straight and crossover cable? This turns straight cat-5 into crossover. Crossover is needed for many different networking applications, the most common of which is to connect two PCs with just the cable. Try doing a little research before being so critical.

static (author)GitarGr82008-03-12

Respectfully, you where a bit sensitive that day, as I noted no criticism.

GitarGr8 (author)static2008-03-12

How dare you call me sensitive!! J/K, it couldn't possibly be that my engineering job has worn down my patience for the uninformed....

static (author)2008-03-12

I had the local network guy make me one of these several years ago. I didn't have the tools nor the cable. I dont know if RS carried them or not. but RS is 50 mile round trip for me if the do. Having the local make me one kept money in my pocket. Good instructable

Randy Lahey (author)2008-02-24

Wow, this is crazy. I made one of these a few years ago when i used to be a computer tech. Very handy. When i made mine I thought to myself "Holy Fuck! what a great idea! I wonder if anyone else thought of this?" It's definitely a must-have for any computer/network techs out there. I'm suprised you can't buy these. p.s. It will also turn a crossover cable into a straight cable.

GitarGr8 (author)Randy Lahey2008-02-25

Apparently you can buy these.

n0ukf (author)GitarGr82008-03-07

But the point of Instructables is DIY and share how you did it. In some cases it's cheaper to buy, in others it's cheaper to make, and in yet other cases, the project isn't available for sale anywhere.

maker12 (author)2008-02-04


vaiden (author)2007-08-21

Man, this is a great instructable. Just the other day I had to cut a damn cat5 cable and swap the tx and rx wires to hook two routers together. Im gonna make one of these bad boys. I dont have gigabit nics, so even though I have a gigabit switch ,I can hum right along without both pairs. Great idea!

The Lightning Stalker (author)2007-07-16

I don't think the keystone jack grabs onto the outer sheath of the cable. This presents a strain relief problem. It might be a good idea to roughen up the sheath near the keystone jack with some sandpaper and dab some flexible drying epoxy around to bond it with the keystone jack. This comes at a loss of the ability to rewire the jack, but should make a more reliable connection since keystone jacks are intended for racks where the wires won't be flexed often.

tsedlmeyer (author)2007-07-10

Great instructable; however, there is one problem with the cable produced.

Unfortunately this cable will not work properly for gigabit ethernet. Gigabit Ethernet utilizes all four pair on the cable. The cable presented here only crosses two of the pair. The correct pinout can be found here. Unfortunately most commercial crossover cables are also not correctly pinned for gigabit ethernet use.

If you use one of these incorrect cables you will still get connectivity on a gigabit ethernet interface; however, you will only get 500Mbs instead of 1000Mbs.

jmumby (author)tsedlmeyer2007-07-14

Gigabit internet does not need a crossover anyway. You can plug any normal network cable and it will just work!

tsedlmeyer (author)jmumby2007-07-15

The spec does not require NICs to detect whether they need to internally cross. Most gigabit ethernet NICs along with many newer fast ethernet NICs do and indeed do not need a crossover cable. Some NICs do not and some disable this feature if you manually set the speed and duplex. Many people manually set speed and duplex for connections such as switch to switch or firewall to router.

tsedlmeyer (author)tsedlmeyer2007-07-10

I should have said may give you connectivity up to 500Mbs. Some chipsets will use the two pair to give you 500Mbs. For instance if you connect two Cisco switches they will do so. Some NIC's will fall back to 100Mbs and some may not provide a connection.

GitarGr8 (author)tsedlmeyer2007-07-10

Great point, I'll edit the instructable to make a note of that.

Wolver (author)2007-07-14

Now why didn't I think of that? Nachos Bellgrande props to Gitar

rimar2000 (author)2007-07-14

Very useful. Good idea, expandable to other applications.

qpmarl (author)2007-07-14

I made one a thems once. Still have it. Never actually used it though. I'm all wireless these days.

Spokehedz (author)2007-07-14

Most punch-down tools have a second end that you use by flipping around the connector. The ends are double-ended as it were.

Also, you can get a retractable CAT-5 cable that will spool up the cable into a neat little box. very handy, and keeps the box nice and neat. - Example of retractable cat-5e cable

mrmath (author)2007-07-09

You get geek points for carrying a straight to crossover converter. I've seen them for sale commercially, but your version offers two advantage. First, the ones I've seen have to have two cables plugged into them, one on each side, so you still need two network cables. Second, you get extra geek points for having made it yourself.

JakeTobak (author)mrmath2007-07-09

The one I bought didn't require 2 cables, but it didn't have any slack like this one does. It was very hard to unplug because of that.
Here's the one I have/had (I don't know where it is)

Jezza Bear (author)2007-07-09

Great Instructable, one of those projects I have never ventured to do, this is certainly a good reference.

farker1 (author)2007-07-09

I have another 2 ways to do this to be used in a 'lightweight' tool kit 1. make a short rj45 plug to plug crossover cable and then use a rj45 socket to socket adapter to join to a straight through cable. The socket adapter can also be used with 2 normal cables to make an extended cable if needed and also rj11 cables to extend modem/router cables 2. buy a socket to socket crossover adapter to be used with 2 normal cables or you can make one with a normal adapter.

brianf25 (author)2007-07-09

ooh so handy.

LasVegas (author)2007-07-09

Great Instructable! Good advice on wiring techniques.

About This Instructable




Bio: Pseudo-intellectual college dropout, with a penchant for snobbery.
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