How to wire your own ethernet cables and connectors. Required:
Here is what the internals of the ethernet cable look like: Show
Internal Cable Structure and Color Coding Inside the ethernet cable, there are 8 color coded wires. These wires are twisted into 4 pairs of wires, each pair has a common color theme. One wire in the pair being a solid or primarily solid colored wire and the other being a primarily white wire with a colored stripe (Sometimes ethernet cables won't have any color on the striped wire, the only way to tell which is which is to check which wire it is twisted around). Examples of the naming schemes used are: Orange (alternatively Orange/White) for the solid colored wire and White/Orange for the striped cable. The twists are extremely important. They are there to counteract noise and interference. It is important to wire according to a standard to get proper performance from the ethernet cable. The TIA/EIA-568-A specifies two wiring standards for an 8-position modular connector such as RJ45. The two wiring standards, T568A and T568B vary only in the arrangement of the colored pairs. Tom writes to say "...sources suggest using T568A cabling since T568B is the AT&T standard, but the US Government specifies T568A since it matches USOC cabling for pairs 1 & 2, which allows it to work for 1/2 line phones...". Your choice might be determined by the need to match existing wiring, jacks or personal preference, but you should maintain consistency. I've shown both below for straight through cabling and just T568B for crossover cabling. About Modular Connector Plugs and Jacks:The 8P8C modular connectors for Ethernet are often called RJ45 due to their physical resemblance. The plug is an 8-position modular connector that looks like a large phone plug. There are a couple variations available. The primary variation you need to pay attention to is whether the connector is intended for braided or solid wire. For braided/stranded wires, the connector has sharp pointed contacts that actually pierce the wire. For solid wires, the connector has fingers which cut through the insulation and make contact with the wire by grasping it from both sides. The connector is the weak point in an ethernet cable, choosing the wrong one will often cause grief later. If you just walk into a computer store, it's nearly impossible to tell what type of plug it is. You may be able to determine what type it is by crimping one without a cable.Modular connector jacks come in a variety styles intended for several different mounting options. The choice is one of requirements and preference. Jacks are designed to work only with solid ethernet cable. Most jacks come labeled with color coded wiring diagrams for either T568A, T568B or both. Make sure you end up with the correct one. Here is a wiring diagram and pin out:
Modular Connector Plug and Jack Pin Out Ethernet Cable Pin Outs:There are two basic ethernet cable pin outs. A straight through ethernet cable, which is used to connect to a hub or switch, and a crossover ethernet cable used to operate in a peer-to-peer fashion without a hub/switch. Generally all fixed wiring should be run as straight through. Some ethernet interfaces can cross and un-cross a cable automatically as needed, a handy feature.Standard, Straight-Through Wiring Diagram(both ends are the same):
Crossover Cable Wiring Diagram:
+Note: The crossover ethernet cable layout is suitable for 1000Base-T operation, all 4 pairs are crossed. How to wire Ethernet Patch Cables:
How to wire fixed Ethernet Cables:
If an ethernet cable tester is available, use it to verify the proper connectivity of the cable. That should be it, if your ethernet cable doesn't turn out, look closely at each end and see if you can find the problem. Often a wire ended up in the wrong place or one of the wires is making no contact or poor contact. Also double check the color coding to verify it is correct. If you see a mistake or problem, cut the end off and start again. A ethernet cable tester is invaluable at identifying and highlighting these issues. When sizing ethernet cables remember that an end to end connection should not extend more than 100m (~328ft). Try to minimize the ethernet cable length, the longer the cable becomes, the more it may affect performance. This is usually noticeable as a gradual decrease in speed and increase in latency. Notes:Power over Ethernet (PoE):Power over Ethernet has been implemented in many variations before IEEE standardized 802.3af. IEEE 802.3af specifies the ability to supply an endpoint device with 48V DC at up 350mA or approximately 16.8W. IEEE 802.3at updates the PoE standard to supply up to 600mA or approximately 28.8W, it is often known as PoE+. The power is delivered using two pairs in the ethernet cable. The device must be capable of receiving power on either the data pairs [Mode A] (often called phantom power) or the unused pairs in 100Base-TX [Mode B]. IEEE 802.3bt further updates the PoE standard to use all four pairs of the cable to deliver up to 90W of power. PoE can be used with any ethernet configuration, including 10Base-T, 100Base-TX or 1000Base-T. Power is only supplied when a valid PoE endpoint is detected by using a low voltage probe to look for the PoE signature on the endpoint. PoE power is typically supplied in one of two ways, either the host ethernet switch provides the power, or a "midspan" device is plugged in between the switch and endpoints and supplies the power. No special cabling is required.
Protocol Details:
4. 30m range.
Related Reading Material
|