Understanding the differences between Class A and Class B cables in networking

Differences between Class A and Class B cables in networking

In network cabling, two well-known standards define the RJ45 pinouts: Class A and Class B. Both specify the color order of RJ45 pins. There is no difference in speed or bandwidth between them; the distinction is purely in the internal color order of wire pairs. These standards correspond to T568A and T568B and are widely used in networking projects.

What is the main difference between Class A and Class B cables?

The key difference lies in the color order of the pins; performance and capability are the same.

Which standard is more common?

In newer projects, T568B is more common; however both standards are official and usable.

Can one end be A and the other B?

Yes. This results in a crossover cable, used for direct device-to-device connections.

What is a Straight cable?

A straight-through cable uses the same standard on both ends (A-A or B-B). It is used to connect devices of different types.

Is there a speed difference between A and B?

No. Speed depends on the cable category (Cat5e, Cat6, etc.), termination quality, and networking equipment, not on choosing A or B.

Color coding of Class A and Class B

Class A:

• 1- White-Green-Green
• 2- White-Orange-Blue
• 3- White-Blue-Orange
• 4- White-Brown-Brown

Class B:

• 1- White-Orange-Orange
• 2- White-Green-Blue
• 3- White-Blue-Green
• 4- White-Brown-Brown

Class A and B in T568A and T568B standards

Class A and Class B cables are defined by two official standards: T568A and T568B. The difference is only in the position of the green and orange wire pairs; there is no difference in speed or quality. The full color sequence for both standards reflects their usage and can be found in a guide to network cable color coding.

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