Nortel Networks 70 Series - Manual (Page 54)

Installation and Reference for the BayStack 70 Series 10/100 Ethernet Switches
B-2 206375-A
Straight-Through and Crossover Cables
For two devices to communicate, the transmitter of each device must be connected
to the receiver of the other device. The crossover function is usually implemented
internally as part of the circuitry in the device. Computers and workstation adapter
cards are usually media-dependent interface ports, called MDI or uplink ports.
Most hub and switch ports are configured as media-dependent interfaces with
built-in crossover ports, called MDI-X or normal ports. Refer to the instructions in
Chapter 3, “Installation,” for appropriate cable use and connection.
Figure B-1 illustrates a straight-through twisted-pair cable.
Figure B-1. Straight-Through Twisted-Pair Cable
Figure B-2 illustrates a crossover twisted-pair cable.
Figure B-2. Crossover Twisted-Pair Cable
MDI port MDI-X port
1
2
3
6
Transmit
Receive
1
2
3
6
Receive
Transmit
Twisted pairs
2008.8
7666EA
1
2
3
6
1
2
3
6
Transmit
Receive
Transmit
MDI-X port MDI-X port
Receive