LAN Wiring & Pinouts

There is NOTHING more annoying than spending 30 minutes debugging a network problem to find it was the cable. Badly made or non-standard cabling is a foolish thing to spend time on - do it once and do it right.

Notes:
1. LAN cables are generically called UTP (Unshielded Twisted Pair) and are identified with a category rating. When installing new cable, unless there is a very good reason not to, you should be using category 5, 5e or 6 UTP which is rated for both 10 and 100mb LAN operation.

2. UTP comes in two forms SOLID or STRANDED. SOLID refers to the fact that each internal conductor is made up of a single (solid!) wire, STRANDED means that each conductor is made up of multiple smaller wires.Beware: Each type of wire, solid or stranded, needs.

3. There is NO excuse with all the choice of color cable and other techniques available to-day for not being able to visually spot the difference between at least a straight and a crossed cable before you spend 1 hour fitting the wrong cable into your network. Disadvantage: You have to remember to put the tubing on BEFORE the connector!

4. You CAN use 100base-TX wiring with a 10base-T network (but not always the other way round). In general ALWAYS use 100baseTX/T4 wiring standards.

5. If you are using category 5, 5e or 6 wiring EVERYWHERE you can use the 100base-TX standard (this only uses 2 pairs , 4 conductors). Most of the information below assumes you are using category 5, 5e or 6 cables.

6. If you are using category 3 or 4 cables with 100M LANs ANYWHERE you MUST use the 100Base-T4 standard and this has ADDITIONAL RESTRICTIONS documented throughout (it uses all 4 pairs, 8 conductors).

7. Maximum LAN cable runs are 100 meters (~300ft).

8. We provide a Cabling FAQ which provides additional information or background.

9. We have added an article on mixing 100 MB LAN and Telephony on a single category 5(e) or 5 cable. It can be done but you must be very cautious.

10. We have updated some of the material for 1000base-T (Gigabit Ethernet 802.3ab) which uses all 4 pairs (8 conductors) and added notes where relevant about Power-over-Ethernet (PoE 802.3af). A copper standard for 10GB Ethernet is being worked on (802.3an) but as of February 2005 the IEEE was still standardizing away.

Category 5(e) (UTP) colour coding table

The following table shows the normal colour coding for category 5 cables (4 pair) based on the two standards supported by TIA/EIA (see also our primer on this topic)

We get occasional email about the difference between 568A and 568B wiring. Which one you use is a matter of local decision. These standards apply to the color code used within any SINGLE cable run - BOTH ENDS MUST USE THE SAME STANDARD. However, since they both use the same pinout at the connectors you can mix 568A and 568B cables in any installation.