T568A and T568B termination – TIA/EIA-568 – Wikipedia
Posted by jpluimers on 2017/08/04
Edit 20260424: Cisco images via Wayback Machine as some of the links had died. Added some extra notes.
Note to self: looking at the various patch cables, it looks like most manufacturers prefer T568B over T568A. Not sure why. I adopted T568B to avoid any confusion.
As I always forget the images on FTP/STP/UTP wiring in both connectors and outlets and forget which standard is T568A and T568B: T568A and T568B termination – TIA/EIA-568 – Wikipedia:
Pin T568A Pair T568B Pair 10BASE-T 100BASE-TX 1000BASE-T Signal ID Wire T568A Color T568B Color Pins on plug face (socket is reversed) 1 3 2 TX+ DA+ tip
white/green stripe
white/orange stripe2 3 2 TX- DA- ring
green solid
orange solid3 2 3 RX+ DB+ tip
white/orange stripe
white/green stripe4 1 1 – DC+ ring
blue solid
blue solid5 1 1 – DC- tip
white/blue stripe
white/blue stripe6 2 3 RX- DB- ring
orange solid
green solid7 4 4 – DD+ tip
white/brown stripe
white/brown stripe8 4 4 – DD- ring
brown solid
brown solidNote that
- the only difference between T568A and T568B is that pairs 2 and 3 (orange/white-orange and green/white-green) are swapped,
- straight cable is T568A↔T568A or T568B↔T568B,
- crossover depends if it is half-crossed or fully-crossed
- rollover is Cisco specific
I will cover the last two in a future blog-post.
For crossover cables (used less and less because of Auto MDI-X which is standard in 10000BASE-T) this is slightly different Appendix B: Ethernet Crossover Cables – Configuring and Troubleshooting Ethernet 10/100/1000Mb Half/Full Duplex Auto-Negotiation – Cisco [WayBack]:
Cisco: Four Twisted-Pair Crossover Cable Schematics for 10/100/1000 and 1000BASE-T GBIC Module Ports
full 10/100/1000Mhz crossover pin-layout
RJ-45 socket pin layout; view from outside in
There are some nice colour coded wiring diagrams at Tech Stuff – LAN Wiring and Pinouts [WayBack] for both straight wiring [WayBack] and crossed wiring [WayBack]:
Note:
- The cisco and tech stuff are fully-crossed: they work fine for CAT5, CAT5E and CAT6.
- Half-crossed work only fine for 10Mhz and 100Mhz ethernet, but not for 1Gz ethernet
--jeroen
The Wiert Corner - irregular stream of stuff 
Leave a comment