Every Cat6 cable contains 8 wires in 4 color-coded pairs. The specific order you place those wires into the RJ45 plug — following either T568A or T568B — determines whether your cable works. This guide covers everything: the color code, what each pair does, T568A vs T568B, how to terminate, and the mistakes that cause failures.
The Cat6 Color Code at a Glance
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The golden rule: The internal wire color code is identical across Cat5e, Cat6, Cat6A, Cat7, and Cat8 — every manufacturer worldwide uses the same four pairs. What changes between categories is the physical construction of the cable, not the colors.
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Orange pair Pair 1 Pins 1 & 2 White/Orange + Orange. Primary data transmit path — carries outgoing signals from your device to the network (TX+ and TX−). TX — transmit |
Green pair Pair 2 Pins 3 & 6 White/Green + Green. Primary data receive path — carries incoming signals from the network to your device (RX+ and RX−). RX — receive |
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Blue pair Pair 3 Pins 4 & 5 White/Blue + Blue. Unused in 10/100 Mbps. In Gigabit Ethernet carries bidirectional data. Also delivers DC power in PoE Mode A. Gigabit bidi |
Brown pair Pair 4 Pins 7 & 8 White/Brown + Brown. Unused in 10/100 Mbps. In Gigabit Ethernet carries bidirectional data. Delivers DC power in PoE Mode B and 4PPoE. Gigabit bidi |
Complete Pin-Out Table (T568B — Standard for Commercial Installs)
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Note: Pins 3 and 6 are both part of the green pair but are not adjacent. This is intentional — the standard splits them to interleave with the blue pair for better crosstalk performance. It’s the most common point of confusion for first-time terminations.
T568A vs T568B: Which Standard Should You Use?
Both T568A and T568B are defined in the ANSI/TIA-568.2-D standard. The only difference is that the orange and green pairs swap positions at pins 1-2 and 3-6. The blue pair (pins 4-5) and brown pair (pins 7-8) are identical in both. Highlighted rows show where they differ.
🟡 Yellow rows = the only positions where T568A and T568B differ.
When to use which: Use T568B for offices, commercial spaces, and new builds in Canada and North America — it’s the dominant standard. Use T568A for residential wiring or when matching an existing T568A installation. Never mix standards on the two ends of the same cable — that creates an accidental crossover cable.
Power over Ethernet (PoE) — Which Pairs Carry Power?
PoE lets a Cat6 cable deliver both data and electrical power to devices like IP cameras, wireless access points, and VoIP phones — no separate power outlet needed.
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Standard Cat6 handles PoE reliably up to 60W. For 90W 4PPoE — common in modern enterprise environments — use Cat6A. Its lower resistance handles higher current without the heat buildup that degrades Cat6 in bundled runs over time.
How to Terminate a Cat6 Cable — Step by Step (T568B)
Tools needed: wire stripper, Cat6-rated RJ45 plugs, crimping tool, cable snips, cable tester.
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1
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Strip the outer jacket — 30–35mm Score the jacket lightly, being careful not to nick the inner wire insulation. Cat6 uses 23AWG conductors — slightly thicker than Cat5e — so adjust your tool’s blade depth accordingly. |
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2
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Remove the center spline and rip cord Cat6 cables contain a plastic X-shaped spline separating the four pairs. Cut it flush with the jacket strip point using snips, along with the rip cord. Do not cut the wires themselves. |
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3
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Untwist pairs — maximum 13mm (½ inch) This is the most critical step for Cat6. The TIA-568 spec allows a maximum of 13mm of untwisted wire at the termination point. Exceeding this introduces crosstalk that causes certification test failures. |
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4
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Arrange wires in T568B order Left to right: White/Orange, Orange, White/Green, Blue, White/Blue, Green, White/Brown, Brown. Hold them flat and parallel. |
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5
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Trim to 13mm and insert into RJ45 plug Cut the aligned wires straight across, leaving 13mm of straight conductor. All eight wires must reach the gold contacts at the front of the plug. Use Cat6-rated plugs — Cat5e plugs are calibrated for 24AWG and may not make reliable contact. |
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6
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Crimp with firm, even pressure Apply steady pressure until the crimping tool clicks. Under-crimping is the single most common cause of intermittent network failures — and it’s impossible to detect visually. |
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7
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Test with a wiremap tester A basic cable tester lights pins 1 through 8 in sequence on both ends. Any miswire — including the “split pair” error where wires from different pairs are accidentally swapped — shows up immediately. Don’t skip this step. |
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Common mistake: Using Cat5e RJ45 plugs with Cat6 cable. Cat6 uses 23AWG conductors; Cat5e plugs are designed for 24AWG wire. The contacts may not pierce the insulation reliably, causing intermittent drops that are very hard to diagnose. Always match your plug rating to your cable category.
Cat6 vs Cat5e, Cat6A, Cat7 & Cat8 — Color Code Differences?
The internal wire color code is identical across all Ethernet cable categories. T568A and T568B apply equally regardless of category. What changes is how the cable is physically built.
Frequently Asked Questions
What are the 4 wire colors inside a Cat6 cable?
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Every Cat6 cable contains four twisted pairs: the orange pair (white/orange + orange), the green pair (white/green + green), the blue pair (white/blue + blue), and the brown pair (white/brown + brown) — eight conductors total. This color system is standardized across all manufacturers and all cable categories from Cat5e through Cat8.
What is the difference between T568A and T568B?
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The only difference is which pairs sit at pins 1-2 and 3-6. In T568B: orange at pins 1-2, green at pins 3 and 6. In T568A: green at pins 1-2, orange at pins 3 and 6. The blue pair (pins 4-5) and brown pair (pins 7-8) are identical in both standards. Both deliver exactly the same electrical performance — the choice is purely about consistency with your existing infrastructure.
Which standard should I use for my Toronto office — T568A or T568B?
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T568B is the dominant standard for commercial installations across North America, including Toronto and the GTA. Most structured cabling contractors, patch panels, and keystone jacks in Canadian offices are terminated to T568B. The most important rule: be consistent — use the same standard on both ends of every cable and throughout the entire installation.
What happens if I mix T568A and T568B on the same cable?
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You create a crossover cable. The transmit pins on one end connect to the receive pins on the other. Modern switches with Auto MDI-X often compensate automatically, but mixing standards causes hard-to-diagnose failures on older equipment, fails cable certification testing, and creates inconsistencies that make future troubleshooting much harder.
Which pairs are used for PoE (Power over Ethernet)?
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Mode A delivers power over the orange and green data pairs (pins 1-2 and 3-6). Mode B delivers power over the blue and brown pairs (pins 4-5 and 7-8). 4PPoE (IEEE 802.3bt, up to 90W) uses all four pairs simultaneously. For 90W 4PPoE, Cat6A is strongly recommended over Cat6 due to heat dissipation requirements in bundled cable runs.
How much can I untwist Cat6 wires when terminating?
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A maximum of 13mm (approximately ½ inch) per the TIA-568 standard. Cat6 is more sensitive than Cat5e because it operates at 250 MHz — even a few extra millimetres of untwist raises near-end crosstalk (NEXT) levels that will cause failure on a Category 6 certification test. Maintain the twist as close to the connector as physically possible.
Does the outer jacket color of a Cat6 cable affect performance?
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No — jacket color has absolutely no effect on speed, bandwidth, or signal quality. A blue Cat6 cable and a yellow Cat6 cable with identical specifications perform exactly the same. Jacket colors are a purely organizational convention IT departments use to identify cable purpose at a glance. Performance is determined entirely by the cable’s category rating and the quality of the termination.