Specifications C-5
RJ-45 Pinouts and Crossover Function
10BASE-T, 100BASE-TX, and 1000BASE-T are keyed systems to differentiate between voice and data transmissions, in order to keep them separate over twisted-pair cable. The Ethernet standard also specifies that each cable segment implement a crossover function to connect the transmitter of one device to the receiver of a device at the other end, and vice-versa. The crossover function may be implemented internally at the hub or switch, or externally, through the twisted-pair media.
10/100 Straight-Through Pinouts
If the crossover function is implemented internally, the port is labeled MDI-X (Medium Dependent Interface–Crossover). When an MDI-X port is connected to an MDI port, the twisted pair media should be wired straight-through using the physical pinouts indicated in Table C-9.
Table C-9
10/100 Pinouts Using Internal, Straight-Through Crossover
Pin | Function | Color Match | Function | Pin |
| | | | |
1 | TD+ | White/Orange | TD+ | 1 |
| | | | |
2 | TD- | Orange/White | TD- | 2 |
| | | | |
3 | RD+ | White/Green | RD+ | 3 |
| | | | |
4 | | Blue/White | | 4 |
| | | | |
5 | | White/Blue | | 5 |
| | | | |
6 | RD- | Green/White | RD- | 6 |
| | | | |
7 | | White/Brown | | 7 |
| | | | |
8 | | Brown/White | | 8 |
| | | | |
Figure C-1. 10/100 straight-through wiring for RJ-45 connector
