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Reference Manual for the Model DG814 DSL Modem Internet Gateway
Networks and Routing Basics B-11
Ethernet Cabling
Although Ethernet networks originally used thick or thin coaxial cable, most installations currently
use unshielded twisted pair (UTP) cabling. The UTP cable contains eight conductors, arranged in
four twisted pairs, and terminated with an RJ45 type connector. A normal "straight-through" UTP
Ethernet cable follows the EIA568B standard wiring and pinout as described in
Table B-3.
Uplink Switches, Crossover Cables, and MDI/MDIX Switching
In the wiring table above, the concept of transmit and receive are from the perspective of the PC,
which is wired as Media Dependent Interface (MDI). In this wiring, the PC transmits on pins 1 and
2. At the hub, the perspective is reversed, and the hub receives on pins 1 and 2. This wiring is
referred to as Media Dependent Interface - Crossover (MDI-X). When connecting a PC to a PC, or
a hub port to another hub port, the transmit pair must be exchanged with the receive pair. This
exchange is done by one of three mechanisms:
• Uplink switch
Most hubs provide an Uplink switch which will exchange the pairs on one port, allowing that
port to be connected to another hub using a normal Ethernet cable.
Table B-3. UTP Ethernet cable wiring, straight-through
Pin Wire color Signal
1 Orange/White Transmit (Tx) +
2 Orange Transmit (Tx) -
3 Green/White Receive (Rx) +
4 Blue
5 Blue/White
6 Green Receive (Rx) -
7 Brown/White
8 Brown