Using the BayStack 450 10/100/1000 Series Switch
E-2 302401-D Rev 00
Table E-1 lists the RJ-45 (8-pin modular) port connector pin assignments.

MDI and MDI-X Devices

Media dependent interface (MDI) is the IEEE standard for the interface to
unshielded twisted pair (UTP) cable.
F or two d ev ices to c ommunicate, t he transmi tter of one device must connect t o the
receiver of the othe r device. The connection is established through a crossover
function, which can be a crossover cable or a port that implements the crossover
function internally.
Ports t hat impl ement t he cros so v er func tion i ntern ally a re known as MDI-X po rts,
where X refers to the crossover function.
The following sections describe the use of straight-through and crossover cables
for connecting MDI and MDI-X devices.
Table E-1. RJ-45 Por t Connector Pin Assignments
Pin Signal Description
1 RX+ Receive Data +
2 RX- Receive Data -
3 TX+ Transmit Data +
4 Not applicable Not applicable
5 Not applicable Not applicable
6 TX- Transmit Data -
7 Not applicable Not applicable
8 Not applicable Not applicable
Note: For the transmitter of one device to connect to the receiver of another
device, the total number of crossovers must always be an odd number.
kombk.book Page 2 Tuesday, June 29, 1999 3:25 PM