T568A vs T568B: Breaking Down Ethernet Wiring Standards

Introduction to T568A and T568B Standards

Getting your wiring standards right is crucial for a functioning network. T568A and T568B define how the eight wires inside Ethernet cables connect to the pins in an RJ45 connector – and choosing the wrong standard can lead to significant headaches down the road.

If you’ve ever found yourself staring at a handful of colorful wires wondering which goes where, you’re not alone. These standards might seem like trivial color patterns, but they’re essential for ensuring your network runs properly.

Both T568A and T568B are officially recognized by the Telecommunications Industry Association (TIA) and Electronic Industries Alliance (EIA). While they look similar at first glance, understanding their differences is important for anyone working with network infrastructure.

What is the Difference Between T568A and T568B?

Here’s the straightforward truth: T568A and T568B are essentially the same standard with the green and orange pairs swapped. In T568A, the green pair connects to pins 1 and 2, while the orange pair connects to pins 3 and 6. T568B reverses this arrangement, with orange on pins 1 and 2, and green on pins 3 and 6. The blue and brown pairs remain in the same positions in both standards.

Let’s break down the wire order:

T568A Wire Order

1. White/Green
2. Green
3. White/Orange
4. Blue
5. White/Blue
6. Orange
7. White/Brown
8. Brown

T568B Wire Order

1. White/Orange
2. Orange
3. White/Green
4. Blue
5. White/Blue
6. Green
7. White/Brown
8. Brown

From a performance standpoint, there’s absolutely no difference between the two standards. Both support identical transmission capabilities and network speeds. The distinction is purely in the wiring arrangement.

Historically, T568A was based on the older USOC (Universal Service Order Code) wiring standard used in telephone systems, providing backward compatibility with both one-pair and two-pair USOC wiring schemes. T568B evolved from AT&T’s 258A standard and became more prevalent in commercial installations.

Cable Termination and Testing

The most common mistake in cable termination isn’t which standard you choose – it’s placing the wrong-colored wire on the wrong pin. One small color mix-up and your network connection fails completely.

When terminating cables, precision matters. The wires must be arranged in the correct order before crimping, and sufficient pressure must be applied with the crimping tool to ensure solid connections. A poorly crimped connection is like a loose handshake – technically a greeting but not inspiring much confidence.

Testing is where professionals distinguish themselves. NetAlly’s network testing tools provide detailed diagnostics:

1. Connect your cable to a NetAlly tester (LinkRunner AT 3000, LinkRunner AT 4000, LinkRunner 10G, or EtherScope nXG)
2. Select the wiring standard you’re using (T568A or T568B)
3. Run the Cable test to validate correct termination
4. Review the results for any wiring errors

If there’s a miswiring, our network testers identify exactly which pins are incorrectly connected, allowing for quick troubleshooting and correction. This level of detail saves hours of frustration trying to diagnose connectivity issues.

Conclusion: T568A vs T568B

Let’s sum up the key points about T568A and T568B:

• The only physical difference is the swap of the green and orange pairs
• Performance is identical between the two standards
• T568A offers better backward compatibility with telephone wiring
• T568B is more commonly used in enterprise environments
• The critical factor is consistency – use the same standard throughout

Best practices for implementation include:

1. Choose one standard and use it consistently in your installation
2. Check regional and industry requirements before starting
3. Test all cables after termination to verify correct wiring
4. Document which standard you’ve used for future reference
5. Consider your organization’s existing infrastructure when selecting a standard

At the end of the day, whether you choose T568A or T568B matters less than implementing it correctly and consistently. Both standards deliver the same performance when properly terminated and tested.

For reliable testing of your network cabling, consider our professional tools:

• LinkRunner AT 3000 – Network Cable & Connectivity Tester
• LinkRunner AT 4000 – Smart Network & Cable Tester
• LinkRunner 10G – Advanced Multi-Gig/10G Cable & Network Tester
• EtherScope nXG – Ethernet Network Tester & WiFi Diagnostics Tool