Quick Answer: A Cat 5e lead ends in an 8P8C plug wired to T568B: white-orange, orange, white-green, blue, white-blue, green, white-brown, brown. Use the same order at both ends, trim the sheath back 0.5 in (13 mm) and push the conductors until they stop, or the contacts will sit on the insulation. A plug rated for 24 to 26 AWG solid or stranded conductor, with a three-prong contact and a proper strain relief, costs a few cents more and is the only part worth buying. Test every lead with a wire map tester before it goes into service.
Most Cat 5e leads that fail in service were never faulty cable. They were terminated with the sheath stripped too far back, the pairs untwisted by 1 in (25 mm) instead of 0.5 in, or the conductors pushed in only two thirds of the way. Each of those mistakes passes a visual check and fails a certification test.
Choosing the plug
Solid or stranded contacts
The contact geometry differs. A plug for solid conductor has two prongs that straddle the wire; a plug for stranded conductor has three prongs that pierce the bundle. Fitting the wrong type gives a connection that measures fine on a continuity tester and fails at 100 MHz, because the contact area is a fraction of the intended one.
Conductor range and load bar
Cat 5e conductors run 24 AWG solid for permanent cable and 26 to 24 AWG stranded for patch leads. A plug specified for 23 to 24 AWG will not grip 26 AWG reliably. A load bar holds the eight conductors in order and stops them moving while the crimp closes; without one, a single conductor shifts and the lead fails intermittently.
Wiring order
T568B, pin by pin
Hold the plug with the clip facing away and count from the left: pin 1 white-orange, pin 2 orange, pin 3 white-green, pin 4 blue, pin 5 white-blue, pin 6 green, pin 7 white-brown, pin 8 brown. Pins 1 and 2 carry one pair, 3 and 6 the second, 4 and 5 the third, 7 and 8 the fourth. That split of pair two across pins 3 and 6 is deliberate and is where most mistakes happen.
A or B, and consistency
T568A swaps the orange and green pairs. Both are valid, both work, and mixing them at the two ends of one lead produces a crossover that will not link. Pick B for new work, record it, and keep it across the site so a later repair does not introduce a second standard.
Pair mapping at a glance
| Pair | Conductors | T568B pins | T568A pins |
|---|
| 1 | White-blue and blue | 4 and 5 | 4 and 5 |
| 2 | White-orange and orange | 1 and 2 | 3 and 6 |
| 3 | White-green and green | 3 and 6 | 1 and 2 |
| 4 | White-brown and brown | 7 and 8 | 7 and 8 |
| Screen | Drain wire if screened | Shell only | Shell only |
Split pairs and testing
A split pair puts one conductor from a pair on pins 1 and 2 and its partner on pins 3 and 6, so the current loop no longer follows a twisted path. Continuity passes on all eight pins and the link may even train at 100 Mbit/s, but crosstalk at 100 MHz is far outside the limit and gigabit will not negotiate. It is the single most common wiring fault found in newly terminated Cat 5e.
A wire map tester shows the fault in seconds as a crossed or reversed pair on the display. A basic continuity tester will not. If the lead is going into a wall, follow the map with a certification test that reports insertion loss and near-end crosstalk, because a wire map cannot see a conductor pushed in only halfway.
Plug body choice matters as much as the contacts. A rj45 connector with a snagless boot protects the clip in a desk environment, and a screened shell helps only when the drain wire is bonded to it. Compare shapes and contact counts in this guide to rj45 plug types before ordering a box of a hundred.
Practical scenarios
- Situation: Fitting plugs to 20 factory leads of 24 AWG solid Cat 5e. Use two-prong solid-conductor plugs, trim the sheath to 0.5 in (13 mm) and keep the pair twist intact to within 0.5 in of the contacts.
- Situation: A rack of 26 AWG stranded cat5e cord leads that keep failing at the boot. Move to a three-prong stranded plug and a moulded relief; crimped plugs on 26 AWG rarely survive daily handling.
- Situation: A gigabit link that negotiates at 100 Mbit/s after a repair. Re-terminate both ends to T568B; a split pair on pins 1, 2, 3 and 6 is the likely cause.
- Situation: A screened Cat 5e run beside a variable-frequency drive. Terminate the drain to the plug shell at both ends and earth the patch panel, or leave the screen unconnected entirely.
FAQ
Can I use a Cat 6 plug on Cat 5e cable?
Yes. A Cat 6 plug accepts the same 24 AWG conductors and its staggered contact layout still lands on the right pins. It costs more and buys nothing at 100 MHz, so plain Cat 5e plugs are the sensible choice.
How far back can the sheath be stripped?
No more than 0.5 in (13 mm) of untwisted conductor, measured from the contact. Every extra half inch of untwisted pair adds crosstalk that shows up as a failed margin at 100 MHz, even when the lead works.
Why do my crimps pull out under load?
Either the conductors were not pushed fully home, or the plug is rated for a larger wire gauge. Both leave the contact resting on insulation. Pull test each lead with about 5 lb of force before accepting it.
