Why we need to crossover

Question

to connect two computers by ethernet crossover wire why we need to crossover the wire internally.

Answer 1

The Crossover Cable allows you to connect two computers directly together by their network cards without using a hub or switch. This type of cable is also needed when connecting a hub or switch together that do not have an uplink port. It is usually made from scratch. It is called a 'crossover cable' because the transmit and recieve pairs are switched (or crossed) at one end.

Answer 2

I'll explain in layman's terms.  A computer's Ethernet port has 8 pins.  Pins 1 and 2 are used to transmit data and pins 3 and 6 are used to recieve data.  If you connect two computers together, you don't want data sent from computer one (pins 1 and 2) to end up at computer two's pins 1 and 2.  Therefore, you need to "cross" the cable over.  the copper wire that is connected to pin 1, computer 1 will be connected to pin 3 computer 2.  The wire connected to pin 2 computer 1, will be connected to pin 6 computer 2.

Answer 3

Imagine a road,

If we drove on the same side in both directions it would be chaos, therefore all of the traffic going "out" one way must be connected to the "in" at the other end, as all sockets are the same the lead must have the crossover in!