Uplink Switches, Crossover Cables, And Mdi/Mdix Switching - NETGEAR WGT634U - 108 Mbps Wireless Storage Router Reference Manual

Preliminary Manual for the 108 Mbps Wireless Media Router WGT634U
Note: Flat "silver satin" telephone cable may have the same RJ-45 plug. However, using telephone
cable results in excessive collisions, causing the attached port to be partitioned or disconnected
from the network.

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 Dependant 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 Dependant 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 two mechanisms. 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. The second method is to use a crossover
cable, which is a special cable in which the transmit and receive pairs are exchanged at one of the
two cable connectors. Crossover cables are often unmarked as such, and must be identified by
comparing the two connectors. Since the cable connectors are clear plastic, it is easy to place them
side by side and view the order of the wire colors on each. On a straight-through cable, the color
order will be the same on both connectors. On a crossover cable, the orange and blue pairs will be
exchanged from one connector to the other.
The WGT634U Wireless Media Router incorporates Auto Uplink technology (also called MDI/
TM
MDIX). Each LOCAL Ethernet port will automatically sense whether the Ethernet cable plugged
into the port should have a normal connection (e.g. connecting to a PC) or an uplink connection
(e.g. connecting to a router, switch, or hub). That port will then configure itself to the correct
configuration. This feature also eliminates the need to worry about crossover cables, as Auto
Uplink TM will accommodate either type of cable to make the right connection.
B-14 Network, Routing, Firewall, and Basics
Preliminary - Go to http://kbserver.netgear.com/products/wgt634U.asp for final manual