10-Base-T Crossover Cable
The following figure shows the correct wiring for a 10Base-T crossover cable
(assuming you're using RJ-45 connectors).
This cable can be used to connect two
computers together without a hub, or to connect two hubs together (without using
an uplink port). If you're connecting two hubs together and one of them has
an uplink port, use a straight cable (rather than the crossover) to connect the uplink
port of one hub to one of the (non-uplink) ports of the other hub.
A bit of technical background: Most computer and workstation network
adapter cards have interface ports referred to as MDI ports (RJ-45 pin
assignments shown on the left side of the above drawing).
"Uplink" ports on hubs have the same pin assignments. Most
normal ports on hubs have MDI-X ports, which use pins 1 and 2 for receive, and
pins 3 and 6 for transmit. A straight cable (one that connects pin 1 to
pin 1, pin 2 to pin 2, etc.) can be used to connect an MDI port (a computer) to
and MDI-X port (a normal port on a hub). Obviously, to connect two MDI
ports together, it is necessary to connect pin 1 to pin 3, pin 2 to pin 6, and
so forth.
To see more detail about the RJ-45 connector, click here.
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