Copper Straight Through Cable: The Everyday Standard
The phrase comes from certification courses, but the object is the cable you already use everywhere.
Quick Answer
| Pin | T568B colour | Role on 10/100 |
|---|---|---|
| 1 | White orange | Transmit plus |
| 2 | Orange | Transmit minus |
| 3 | White green | Receive plus |
| 6 | Green | Receive minus |
| 4, 5, 7, 8 | Blue and brown pairs | Unused at 10/100, used by gigabit |
Each pin connects to its same number at the far end. That is the entire definition.
Where Straight Through Is Used
Computer to switch or router
The standard case. MDI port to MDIX port.
Switch to router
Also dissimilar port types, also straight.
Anything modern
Auto MDIX makes the wiring choice irrelevant on new equipment.
Gigabit note
Gigabit uses all four pairs, so damage to any pair matters.
Verification
- Compare colour order at both ends.
- Identical order confirms straight through.
- Test with a wiremap tester for certainty.
- Confirm the negotiated speed after installation.
- Replace, not re-terminate, when in doubt about old runs.
Real-World Applications
- Every desk connection.
- Home router to computer links.
- Rack patching.
- Certification practice.
Related Guides
For the colour code, read Cat5e colour code. For the crossover counterpart, see crossover Ethernet cable. For patch leads, start with what is a patch lead.
FAQ
Is straight through the same as normal cable?
Yes. It is the default wiring for Ethernet.
Which standard should I terminate to?
T568B is the common convention. Use one standard throughout an installation.
Does gigabit need different wiring?
No, the same order. Gigabit simply uses all four pairs.
What happens if I mix A and B?
You have made a crossover, which modern ports handle anyway.