Ethernet Cable Color Coding and Crimping
Introduction
Ethernet cables (Cat5e, Cat6, Cat6a, etc.) use twisted pairs of wires inside to carry data. The way these wires are arranged and connected to the RJ45 connector follows strict standards — mainly T568A and T568B. Getting the wiring wrong causes connection failures, slow speeds, or no link at all.
This guide explains both standards, shows straight-through vs crossover cables, provides clear color code diagrams, and walks you through crimping RJ45 connectors and punching keystone jacks / patch panels.
T568B Straight-Through Cable
This is the most common wiring standard used today for connecting computers to switches/routers (straight-through cable). Both ends use the same order (T568B).
| Pin | Color | Wire Name |
|---|---|---|
| 1 | White/Orange | Orange Stripe |
| 2 | Orange | Orange Solid |
| 3 | White/Green | Green Stripe |
| 4 | Blue | Blue Solid |
| 5 | White/Blue | Blue Stripe |
| 6 | Green | Green Solid |
| 7 | White/Brown | Brown Stripe |
| 8 | Brown | Brown Solid |
T568B and T568A Crossover Cable
Crossover cables connect two similar devices directly (e.g., PC to PC, switch to switch) without a hub/switch. One end uses T568B, the other uses T568A to swap transmit/receive pairs.
Modern devices with Auto-MDI/MDIX support usually don't need crossover cables anymore — but older equipment still does.
RJ45 Color Code for 2 Pairs (Fast Ethernet)
Fast Ethernet (100 Mbps) only uses 2 pairs (pins 1-2 and 3-6). Gigabit Ethernet uses all 4 pairs.
Common in older installations or when only 100 Mbps is needed.
Step-by-Step RJ45 Crimping Procedure
- Strip the outer jacket of the cable (about 1–1.5 inches).
- Untwist and straighten all four pairs of wires.
- Arrange the wires in the correct order (T568B or T568A) — hold them flat and tight.
- Cut the wires evenly, leaving about 0.5 inch exposed from the sheath.
- Insert the wires fully into the RJ45 connector (make sure they reach the end).
- Check that the wires are in the correct pin order and fully seated.
- Crimp the connector firmly with a crimping tool.
- Repeat on the other end using the same standard (for straight-through) or opposite (for crossover).
After crimping, always test the cable with a cable tester to confirm continuity and correct wiring.
I/O Port (Keystone Jack) Punching Color Code
When punching down cables into keystone jacks, patch panels, or wall plates, follow the same T568A or T568B standard on both ends.
Most keystone jacks have color-coded pins labeled for both T568A and T568B — choose one standard and be consistent on both ends.
Quick Reference: T568B vs T568A Pinout
T568B Color Code
| Pin | Color | Wire Name |
|---|---|---|
| 1 | White/Orange | Orange Stripe |
| 2 | Orange | Orange Solid |
| 3 | White/Green | Green Stripe |
| 4 | Blue | Blue Solid |
| 5 | White/Blue | Blue Stripe |
| 6 | Green | Green Solid |
| 7 | White/Brown | Brown Stripe |
| 8 | Brown | Brown Solid |
T568A Color Code
| Pin | Color | Wire Name |
|---|---|---|
| 1 | White/Green | Green Stripe |
| 2 | Green | Green Solid |
| 3 | White/Orange | Orange Stripe |
| 4 | Blue | Blue Solid |
| 5 | White/Blue | Blue Stripe |
| 6 | Orange | Orange Solid |
| 7 | White/Brown | Brown Stripe |
| 8 | Brown | Brown Solid |
Conclusion
Correct Ethernet cable wiring using T568B (or T568A consistently) is essential for reliable network connections. Use T568B for new installations — it's the modern standard. Always test every cable you make with a cable tester before deploying it.
Double-check color order before crimping — fixing a bad cable is much harder after it's installed in walls or ceilings.