For a straight-through Ethernet cable, terminate both ends as T568A or both ends as T568B. The two schemes swap the green and orange pairs; the blue and brown pairs stay on the same pins. Neither scheme provides a speed advantage over the other.
Before using a color chart, confirm the connector’s orientation. A correct sequence read from the wrong side produces an incorrect termination.
RJ45 Plug Orientation and Pin Numbers
Use the following viewing position for every plug color sequence on this page:
- Hold the plug with its flat gold-contact surface facing up toward you.
- Keep the latch underneath, away from your view.
- Point the plug’s mating end away from you, with the cable entering from the end nearest you.
- Read the contacts from left to right: pin 1 through pin 8.
This is a top view of the contact surface—not a head-on view into the plug’s mating end.
| Position in this top view | Far left | Far right | ||||||
|---|---|---|---|---|---|---|---|---|
| Contact number | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
When comparing two terminated plugs, place both in this same orientation. Do not reverse one plug to make the cables point in opposite directions.
Do not copy a jack’s rear terminal layout onto a plug
A keystone jack or patch panel may arrange its rear insulation-displacement contacts differently from the numbered contacts at the front. Follow that product’s T568A or T568B termination labels.
Fluke Networks specifically notes that rear jack layouts vary by manufacturer: internal connections route those terminals to the correct front contacts. A plug pinout is therefore not a universal left-to-right punch-down diagram.
T568A and T568B Pinout Chart
“White/green” means a white conductor with a green stripe; “green” means the predominantly solid-green conductor. The same convention applies to the other colors.
The table lists plug contacts in the viewing orientation defined above. Fluke Networks identifies the green pair on pins 1–2 for T568A and the orange pair on pins 1–2 for T568B; the other of those two pairs occupies pins 3 and 6.
| Pin | T568A conductor | T568B conductor |
|---|---|---|
| 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 |
The physical twisted pairs must remain assigned to these contact groups:
- Pins 1 and 2
- Pins 3 and 6
- Pins 4 and 5
- Pins 7 and 8
Notice that pins 3 and 6 form one pair even though pins 4 and 5 sit between them. Do not arrange all four pairs as adjacent two-wire blocks. That creates incorrect pair assignments rather than a valid alternative pinout.
Which scheme should you choose?
Follow the project specification and match the documented scheme on the link you are extending or repairing. If no scheme is specified, select one and use it consistently for the fixed cabling and its documentation.
T568A and T568B have equivalent transmission performance when correctly implemented. Choosing T568B instead of T568A does not turn a cable into a higher category or increase its Ethernet speed capability.
The critical distinction is between using different schemes on separate, correctly terminated links and using different schemes at opposite ends of the same cable. The latter changes the end-to-end wire map.
Straight-Through vs. Crossover Wiring
A straight-through cable preserves every contact number from end to end. A conventional T568A-to-T568B crossover exchanges the pairs on pins 1–2 and 3–6, while leaving the blue and brown pairs unchanged. Cisco documents this pair exchange when identifying crossover cables.
| Pin at end 1 | Pin at end 2: straight-through | Pin at end 2: T568A-to-T568B crossover |
|---|---|---|
| 1 | 1 | 3 |
| 2 | 2 | 6 |
| 3 | 3 | 1 |
| 4 | 4 | 4 |
| 5 | 5 | 5 |
| 6 | 6 | 2 |
| 7 | 7 | 7 |
| 8 | 8 | 8 |
Straight-through: T568A–T568A or T568B–T568B
Use the same scheme at both ends of an ordinary straight-through cable. Both combinations produce the same numbered wire map:
1 → 1, 2 → 2, 3 → 3, 4 → 4, 5 → 5, 6 → 6, 7 → 7, 8 → 8.
The conductor colors differ between an A–A cable and a B–B cable, but the electrical contact-to-contact relationship does not. Cisco defines straight-through wiring by this matching pin-number relationship.
A correctly wired B–B patch cord can therefore connect to a correctly wired A–A permanent link without introducing a crossover: each segment preserves the same contact numbers.
Crossover: T568A at one end, T568B at the other
An A–B cable creates the two-pair crossover traditionally used for 10BASE-T and 100BASE-TX connections between ports that require their transmit and receive pairs to be exchanged.
Do not treat this A–B pattern as a universal crossover specification for every Ethernet interface. Cisco distinguishes two-pair crossover wiring for 10/100 ports from four-pair crossover wiring for 1000BASE-T ports. For equipment requiring a manual crossover, use the pinout specified in its hardware documentation.
Check Auto-MDI-X before making a special cable
Auto-MDI-X allows a supported port to detect the required straight-through or crossover relationship and adjust internally. Cisco’s IE 3010 documentation permits either cable type on the listed copper interfaces when this feature is enabled. That is a device-specific capability, not a reason to assume every port supports it or has it enabled.
For current equipment, check the port documentation and configuration before making a crossover cable. Use an ordinary straight-through cable unless the equipment or application specifically calls for another wire map.
Terminating Plugs, Jacks, and Patch Panels
The pinout tells you where each conductor must connect. It does not establish whether a particular plug fits a particular cable.
Before termination, identify:
- The required wiring scheme and intended end-to-end wire map.
- The cable and connector part numbers.
- The connector manufacturer’s cable compatibility requirements.
- The specified preparation, conductor-routing, termination, and inspection procedure.
Use the connector instructions for strip length, conductor preparation, load-bar arrangement, and tooling rather than applying one generic preparation dimension to every product. Belden notes that cable preparation and termination aids vary with connector and cable construction and can affect termination quality.
For a plug, arrange the conductors using the pinout table, then recheck the viewing orientation before completing the termination.
For a jack or patch panel, use the selected A or B markings on that exact component. Do not count rear terminals from left to right and assume they correspond directly to front pins 1 through 8.
Preserve the cable’s pair construction during preparation and follow the manufacturer’s limits on untwisting and handling. Belden warns that flattening, damaging, or excessively untwisting conductors can change electrical characteristics and impair performance even when the final color order looks correct.
Test the Wire Map—Not Just the Colors
Inspecting conductor colors is useful, but it does not confirm that every contact has made a reliable connection.
After termination, check the complete cable or link with a suitable tester. For a straight-through assembly, the expected result is all eight contacts connected to their matching numbers at the far end, with the correct pair assignments.
A continuity pass can still hide a split pair
A split pair occurs when conductors from different physical twisted pairs occupy positions that should belong to one pair. If the same mistake is repeated at both ends, a simple continuity tester may still show 1 → 1 through 8 → 8.
For example, placing the solid-blue conductor on pin 6 and the solid-orange conductor on pin 4 at both ends of an otherwise T568A-ordered cable preserves numbered continuity but breaks the physical pair assignments on 3–6 and 4–5. Fluke Networks uses this type of fault to explain why split-pair detection provides information that a simple LED continuity tester does not.
Use a tester that explicitly detects split pairs when checking pair integrity. Auto-MDI-X is not a substitute for this test: its documented role is to accommodate straight-through and crossover connections, not repair arbitrary conductor or pair errors.
Interpret the result against the intended cable type
| Test result | What to check |
|---|---|
| Open conductor | Check whether the conductor is fully seated and contacted, and inspect for a break. |
| Short circuit | Inspect the affected termination or cable for unintended conductor contact. |
| Unexpected crossed conductors | Compare both ends against the intended pinout; do not assume every cross is a valid crossover. |
| Split pair | Restore the physical pairs to 1–2, 3–6, 4–5, and 7–8. |
| Correct straight-through wire map | Continue with the performance testing required for the installation; wire map alone does not establish cable-category performance. |
If intentionally testing a crossover cable, select the appropriate crossover configuration and test limit on the tester. Fluke Networks documents this requirement for its DSX CableAnalyzer; an intentional crossover should not be judged against an ordinary straight-through wire-map expectation.
A working link light or a correct wire map answers a narrower question than a cabling performance test. Neither, by itself, establishes that the installed link meets its specified category or supports every intended operating condition.
Printable Wiring Reference
Print the pinout and wire-map tables above using your browser’s print command. The conductor names remain usable in black and white; the reference does not depend on colored cells.
Keep the orientation instructions with the printed pinout. A detached color sequence without its viewing direction is easy to misapply.
For a field record, note the cable identifier, scheme at each end, intended straight-through or crossover map, and tester result. For jacks and patch panels, retain the component’s own termination instructions alongside this reference rather than substituting the plug chart for its rear-terminal labels.