The TIA/EIA-568 specifies two wiring standards for a 8-position modular connector for network connections. The two wiring standards, T568A and T568B vary only in the arrangement of the colored pairs. The only difference is in the orange and green pairs, for wire colors. You can use either standard, as the signals don't care what the colors are, just that you keep to the standard at each end. Your choice might be determined by the need to match existing wiring, jacks or personal preference, but you should maintain consistency. Sources suggest either way. Just to give you another (confusing) decision, sources indicate that traditionally B is used because of the AT&T 258A standard, however, The U.S. N.C.S. Federal Telecommunications recommendations do not recognize B. US Government specifies A since it matches USOC cabling for pairs 1 & 2, which allows it to "work for 1/2 line phones...". There's more on this point at the end of this page.

A straight through cable is used to connect DTE-to-DCE or DCE-to-DTE devices, like a hub or switch, or a NIC (in a PC) to a switch, because they are unlike devices. The wires are is just that; pin-for-pin on each end of the patch cable are the same colors, therefore, the transmit and receive wires are straight through. You can identify a straight through cable by holding both plugs (ends of the cable) side-by-side, in the same orientation. For example, hold both plugs with the locking clip pointing down and the cable pointing towards you. The color of wires will be the same on each plug. If a cable does not say crossover, it is a probably a standard patch cable. More on this thought, later.

A cross over is used to connect DTE-to-DTE or DCE-to-DCE devices, like two NICs, (each inside two PCs) because they are like devices. An ethernet crossover cable has it's send and receive wires crossed. This type of connection in a peer-to-peer fashion can be done without a hub/switch. This is rather common in home networks.

Watch out !

Products sometime surprise you and cause confusion, so be ready. For example, when using a hub or switch, this is automatically done for you, so in that case you would not use a cross over cable. Some interfaces can cross and un-cross a cable automatically as needed, which can really quite nice, in a way, or cause confusion, when adding other devices to the mix. Examples would be cable and DSL modems that have their actual ethernet plugs/jacks (perhaps) reversed. This is to allow people to hook up a cable modem to a computer without this (special) crossover cable. TIP: If you run into trouble and your devices are not working, you might try a different cable standard in case the auto-crossover in some devices is "hosing" you up.

Again, you can identify a cross over cable by holding both plugs (ends of the cable) side-by-side, in the same orientation. In this case, the color of wires will not same on each plug, left to right. You'll notice the green and orange pairs have been rolled, while the blue and brown pairs are straight as in the picture shows. As mentioned earlier, a crossover cable is not to be confused with a "roll over" cable, which is not covered here. The other pictures shows the alternative by using a cross over adaptor, with a straight through cable. Either way accomplishes the same task.

The Author uses way to remember which is by thinking that a crossover cable is the same as terminating one end with 568-A , while the other end with 568-B standard. When making up your own cables, the Author uses two other methods, which are to label them and/or use different color cables for each type.

The most popular crossover cables made are:

What You Need:
Required:
CAT 5 Cable - bulk Category 5, 5e or 6 cable
8P8C male ends
Crimper for them
Wire Cutters - to cut and strip the cable if necessary
There is also a pull string inside the group of wire pairs for the same reason.

Also Recommend:
Wire Stripper
Cable Tester

About the Cables and the Connectors for them:

Most professionals will advise you do not build your own cable, but rather to purchase factory made cables. It's an art to build a proper cable and connector. This will keep another variable in a troubleshooting nightmare, in the event this should happen to you. If you still choose to build your own you will need to know about cables, and the connectors for them. You can find bulk supplies of the cable at many computer stores or most electrical or home centers. You want UTP (Unshielded Twisted Pair) Category 5 cable for basic 10/100 functionality. You should run CAT5e whenever possible because there is usually not a cost difference from CAT5 if you look hard enough. Moreover, if you install higher rated cable, now it will give you a measure of future proofing.

Bulk cable comes in 2 basic categories, solid and braided cable. Braided cable tends to work better in "patch" applications for desktop use. It is more flexible and resilient than solid cable and easier to work with, but really meant for shorter lengths. Solid cable is meant for longer runs in a fixed position. Plenum rated cable should/must be used whenever the cable travels through an air circulation space. For example, above a false ceiling or below a raised floor. At the store it may be difficult or impossible to tell from the box. If you're lucky the salesperson will permit you to open up an end for inspection.

Connectors come in the 2 type as well; for solid and braided cable. Generally speaking if you mix the two types up you will run into big trouble. The main "don't" is using a stranded connector for sold cable. It's unknown if it's visa-vers at this time. At any rate you need to know the difference. The connector have little "prongs" on the crimp that need to provide a low resistant connection to the cable's conductors. You may find conflicting information, however presently, the Author understands that a connector for stranded cable has one little prog that will bite/bury itself into the strand of the wire. The connector for solid has two little "sub-prongs" that will bit on each side of the single conductor. With a microscope you may be able to see the difference.

100 meters (about 330 feet) is your maximum distance for most twisted pair ethernet, with the exception of the latest type as discussed earlier. For longer distances you could install a switch, or some other device as a "buffer". Also, (copper cable) Ethernet to FOC (Fiber Optical Cable) media converters are starting to come down in price. When 100 meters is not enough distance, an ethernet to FOC media converter can be placed on each end making the maximum distance something like 40km. Another use for FOC is electrical insulation. Some people like to run cables underground between homes. If you run CAT5 cable, the homes have different 'ground potentials' and you can burn out network card during an electrical storm. One solution is FOC . Run FOC between the homes or run a pair of FOC converters on one end of the cable with a short FOC run. This will electrically separate the two homes. The Author does not run FOC between buildings and has been fortunate, so far, during lighting. The bottom line is you can make longer runs; just be prepared to have additional problems and issues. It's up to you.

Connectors:

After crimping the modular ends verify the wires ended up the right order and that the wires extend to the front of the connector and make good contact with the metal contacts. Cut the cable to length - make sure it is more than long enough for your needs. Remember, an end to end connection should not extend more than 100m (~328ft). Try to keep cables short, the longer the cable becomes the more it may affect performance, usually noticeable as a gradual decrease in speed and increase in latency. If a cable tester is available, use it to verify the proper connectivity of the cable. That should be it, if your cable doesn't turn out, look closely at each end and see if you can find the problem. Usually a wire ended up in the wrong place or more commonly, one of the wires didn't extend to the front of the modular connector and is making no, or poor contact. If you see a mistake or problem, cut the end off and start again.