Let‘s start with the key thing you really need to know: 568A and 568B are competing standards that define how the colored wires are arranged inside Ethernet cable RJ45 connectors.
I know – that‘s a very technical definition. Let me explain what it means in plain English.
Inside every Ethernet cable are eight tiny copper wires, grouped into four pairs. Each wire pair is twisted together to help reduce interference. The wire pairs have colored insulation – orange, green, blue and brown – so you can tell them apart.
The 568 standards define which wire color is connected to each pin inside the RJ45 plug at each end of the cable.
So why are there two competing standards for something that seems so basic? Keep reading to uncover the method behind the madness.
A Quick History of 568A and 568B
The 568A and 568B standards trace their roots back to the early 1990s. That‘s when the Telecommunications Industry Association (TIA) first published the TIA/EIA-568 standard for commercial building cabling systems. This included the original T568A and T568B wiring pinouts for Ethernet cables with RJ45 connectors.
Over the years those standards evolved into what we now know as 568A and 568B. The wiring scheme has stayed the same, but the names were simplified.
The first iteration, 568A, was defined in 1991. Then in 1993 the TIA published 568B as an alternative arrangement. The goal was continued hardware compatibility as Ethernet speeds increased from 10Mbps to 100Mbps and eventually 1Gbps.
How are these two wiring standards still living side-by-side 30 years later? Well, each one does offer certain advantages depending on your network environment and equipment…
Key Comparisons Between 568A and 568B
Beyond the high level overview, let‘s dig into the nitty gritty details comparing these two standards:
Compatibility
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568A – Offers backward compatibility with phone systems using USOC (Universal Service Order Codes) wiring. Recommended for older telephony equipment.
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568B – Incompatible with USOC wiring but universally supported by networking hardware. Recommended for modern Ethernet environments.
Commonalty
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568A – The original standard published in 1991. Was more widely adopted early on.
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568B – Defined two years after 568A. Has emerged as the more popular wiring scheme on modern equipment.
Noise Resistance
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568A – Provides adequate noise cancellation for 10/100Mbps networks.
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568B – Arrangement results in better noise rejection, an advantage for 1Gbps networks.
So in summary:
- 568A is the "legacy" option – works with older gear but performance limited
- 568B is the "modern" wiring suited for high speeds and latest hardware
Pinout Arrangement
One core difference between 568A and 568B is the actual wire pinout termination defined for RJ45 plugs:
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| Pin Number | 568A Termination | 568B Termination |
|---|---|---|
| 1 | White/Green | White/Orange |
| 2 | Green | Orange |
| 3 | White/Orange | White/Green |
| 4 | Blue | Blue |
| 5 | White/Blue | White/Blue |
| 6 | Orange | Green |
| 7 | White/Brown | White/Brown |
| 8 | Brown | Brown |
So the green and orange wire pairs are swapped between 568A and 568B – but otherwise the blue/brown pairs go to identical pins. Keep this straight in your head and you‘ll be way ahead of the game.
Real-World Implications: Does it Really Matter?
At this point you might be wondering – if 568A and 568B ultimately deliver electrons just fine over Ethernet, why should I care which one I use?
That‘s an excellent question! When it comes to basic patch cables between your computer and office wall jack, generally no – it does not matter. Nearly all modern IT gear supports both wiring schemes thanks to a technology called Auto MDI-X.
But there are some specific cases where using the same 568 standard end-to-end becomes important:
- Interconnecting older network hardware that lacks Auto MDI-X – mixing standards can cause issues
- Consistency across telecom rooms and patch panels is mandatory – can‘t mix 568A and 568B
- Direct connections between computers without a switch uses Ethernet crossover cables (568A to 568B) to function correctly
Additionally, while both standards technically work for modern networks, 568B should be preferred whenever possible because:
- It‘s universally compatible with latest networking equipment
- Offers improved noise cancellation benefits at higher speeds
- Has emerged as the de facto standard for new installations
For best practice on any job, prevent headaches down the road by sticking with 568B across all your new copper cabling and components. And if extending older infrastructure cabling, make 100% sure to continue whichever 568 standard is already in use.
Real-World Recommendations
Hopefully the background helps explain why two competing Ethernet wiring standards even exist 30 years later – and why it still matters in certain cases.
When it comes time to actually buyEthernet cables and install them, what do the 568 standards mean for you? Follow these tips:
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Buying brand new patch cables? Any old cable will work great since modern cords are always wired 568B on both ends.
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Installing new infrastructure cabling and jacks? Verify components are spec‘d for 568B wiring. Stick with B end-to-end.
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Integrating with old equipment? Use cables with 568A termination if needed for compatibility.
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Direct networking two computers? Get a crossover patch cord cable with 568A on one end, 568B on the other.
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Testing existing cabling? Use a cable tester to verify if wiring is 568A or 568B standard. Keep infrastructure consistent!
If you apply those practical rules, you‘ll avoid any issues related to Ethernet wiring standards.
Let me know if any other cabling questions come up! Having the right cables in place goes a long way toward keeping both our networks running smoothly.
