Lab 5.3.4 Crossover Cable

Estimated time: 30 min.

Objectives:

- Build a crossover Ethernet patch cable to T568-B (or T-568-A) standards for connection from workstation to workstation or from switch to switch.

Background:

> In this lab you will learn how to build a Category 5 (CAT 5) Unshielded Twisted Pair (UTP) Ethernet crossover network cable and test it for good connections (continuity) and correct pinouts (correct color of wire on the right pin). This will be a 4-pair (8-wires) "crossover" cable which means that pairs 2 and 3 on one end of the cable will be reversed on the other end. It will be wired to TIA/EIA-568-B and A standards for 10BASE-T Ethernet which determines what color wire is on each pin. The pinouts will be T568-A on one end and T568-B on the other end. All 8 conductors (wires) should be terminated with RJ-45 modular connectors.

> This patch cable will conform to the structured cabling standards and, if it is used between hubs or switches, is considered to be part of the "vertical" cabling also know as backbone cable. A crossover cable can be used as a backbone cable to connect two or more hubs or switches in a LAN or to connect 2 isolated workstations to create a mini-LAN. This will allow you to connect two workstations together or a server and a workstation without the need for a hub between them. This can be very helpful for training and testing. If you want to connect more than two workstations you will need a hub or a switch.

Tools / Preparation:

> Prior to starting the lab, the teacher or lab assistant should have a spool of Cat 5 Unshielded Twisted Pair (UTP) cable, RJ-45 (8-pin) connectors, a RJ-45 crimping tool and an Ethernet / RJ-45 continuity tester available. Work individually or in teams. The following resources will be required:

> - Two to three foot length of Cat 5 cabling (one per person or one per team)
> - Four RJ-45 connectors (two extra for spares)
> - RJ-45 crimping tools to attach the RJ-45 connectors to the cable ends
> - Ethernet cabling continuity tester which can test crossover type cables (T568-A to T568-B).
> - Wire cutters

Step 1 – Create a crossover patch panel cable.

> Use the following tables and diagrams and steps to create a crossover cable. One end of the cable should be wired to the T568-A standard and the other end to the T568-B standard. This crosses the transmit and receive pairs (2 and 3) to allow communication to take place. Only four wires are used with 10BASE-T or 100 BASE-TX Ethernet:

> T568-A Cabling

> Pin# | Pair# | Function | Wire Color | Used with 10/100 BASE-T Ethernet? | Used with 100 BASE-T4 and 1000 BASE-T Ethernet?
> 1 | 3 | Transmit | White/Green | Yes | Yes
> 2

3
Transmit
Green/White
Yes
Yes
3 | 2 | Receive | White/Orange | Yes | Yes
4 | 1 | Not used | Blue/White | No | Yes
5 | 1 | Not used | White/Blue | No | Yes
6 | 2 | Receive | Orange/White | Yes | Yes
7 | 4 | Not used | White/Brown | No | Yes
8 | 4 | Not used | Brown/White | No | Yes

T568-B Cabling

Pin# | Pair# | Function | Wire Color | Used with 10/100 BASE-T Ethernet? | Used with 100 BASE-T4 and 1000 BASE-T Ethernet?
1 | 2 | Transmit | White/Orange | Yes | Yes
2 | 2 | Transmit | Orange/White | Yes | Yes
3 | 3 | Receive | White/Green | Yes | Yes
4 | 1 | Not used | Blue/White | No | Yes
5 | 1 | Not used | White/Blue | No | Yes
6 | 3 | Receive | Green/White | Yes | Yes
7 | 4 | Not used | White/Brown | No | Yes
8 | 4 | Not used | Brown/White | No | Yes

1. Determine the distance between devices, or device and plug, then add at least 12" to it. The maximum length for this cord is 3 m; standard lengths are 6' and 10'.
2. Cut a piece of stranded Cat 5 unshielded twisted-pair cable to the determined length. You will use stranded cable for patch cables because it is more durable when bent repeatedly. Solid wire is fine for cable runs that are punched down into jacks.
3. Strip 2" of jacket off one end of the cable.
4. Hold the 4 pairs of twisted cables tightly where jacket was cut away, then reorganize the cable pairs into the order of the 568-B wiring standard. Take care to maintain the twists since this provides noise cancellation. (orange pair, green pair, blue pair, brown pair)
5. Hold the jacket and cable in one hand, untwist a short length of the green and blue pairs, and reorder them to reflect the 568-B wiring color scheme. Untwist and order the rest of the wire pairs according to the color scheme.
6. Flatten, straighten, and line up the wires, then trim them in a straight line to within 1/2" - 3/4" from the edge of the jacket. Be sure not to let go of the jacket and the wires, which are now in order! You should minimize the length of untwisted wires because overly-long sections that are near connectors are a primary source of electrical noise.
7. Place an RJ-45 plug on the end of the cable, with the prong on the underside and the orange (green on the 586-A end) pair to the left side of the connector.
8. Gently push the plug onto wires until you can see the copper ends of the wires through the end of the plug. Make sure the end of the jacket is inside the plug and all wires are in the correct order. If the jacket is not inside the plug, it will not be properly strain relieved and will eventually cause problems. If everything is correct, crimp the plug hard enough to force the contacts through the insulation on the wires, thus completing the conducting path.
9. Repeat steps 3-8 to terminate the other end of the cable, using the 568-A scheme to finish the crossover cable.
10. Test the finished cable and have the instructor check it. How can you tell if your cable is functioning properly?