Crossover LAN Cable Wiring: From Spool to Tester
Building any Ethernet cable is the same skill. A crossover only adds the decision about which end follows which standard.
Quick Answer
Strip the jacket, untwist the pairs minimally, terminate one end to T568A and the other to T568B, crimp with an RJ45 plug, then test with a wiremap tester. The tester should show a crossover pattern: pins 1 and 3 mapped together, pins 2 and 6 mapped together, and the remaining pins straight.
Tools and Materials
| Item | Purpose |
|---|---|
| Cable, Cat5e or better | The medium |
| RJ45 plugs | Termination, rated for solid or stranded as appropriate |
| Crimping tool | Seats the contacts |
| Stripper or careful knife | Removes the jacket without nicking conductors |
| Wiremap tester | Confirms pin order |
Step by Step
Strip and sort
Remove 25 millimetres of jacket, separate the four pairs, and untwist as little as possible.
Arrange to the standard
Line the conductors in the A order at one end, B order at the other, and cut them level.
Crimp
Push the conductors fully home, confirm order through the plug’s transparent body, then crimp.
Repeat and test
Terminate the second end, then test. A correct crossover shows the 1 to 3 and 2 to 6 mapping.
Common Faults
- Wrong order at one end, showing as a wiremap fault.
- Conductors not fully seated, showing as an open pin.
- Jacket not clamped, leading to failures when the cable is pulled.
- Excessive untwist, reducing high speed performance.
- Nicked conductors from a careless strip.
Real-World Applications
- Making a specific length for a legacy link.
- Replacing a damaged end in place.
- Training termination skills on a bench.
- Preparing lab cabling.
Related Guides
For the standards, read crossover Ethernet wiring. For the cable’s use, see crossover Ethernet cable. For straight through practice, start with Cat5e colour code.
FAQ
Which end is which?
It does not matter, as long as one end is T568A and the other T568B.
What should the tester show?
A 1 to 3 and 2 to 6 pair mapping, with the rest straight.
Can I use Cat6?
Yes, with plugs rated for the conductor gauge.
Why does my cable fail at gigabit only?
Usually excessive untwist or a marginal termination that passes at lower speeds.