A crossover cable, sometimes refered to as a x-over or a crossconnect is an
Ethernet cable that in addition to allowing the direct connection of NICs also allows
hubs and
switches to be directly connected.
Here's the pinout for an x-over with a standard RJ-45 jack.
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Also note that only pins 1,2,4, and 6 are needed in a 10-BaseT half duplex environment. I usually just dike the other four wires out before crimping. It makes it easy to tell your crosses from your standard Ethernet patch cables.