Crossover cable pinout

[PietroPoliseno27977]

Hello everyone on the official cisco documentation it is written that the switch transmits on pins 3 and 6 and receives on pins 1 and 2; it also shows the graph of the crossing of the wires from one end to the other, also explaining that both transmit on pins 3 and 6 and receive on pins 1 and 2. Now leaving out for a moment that the current devices recognize if the cable is wrong and therefore they modify the logic of transmission reception, however on the internet I have read several articles explaining that in the case of two switches while switch A transmits with pins 3 and 6 and switch B receives on pins 1 and 2 (so far according to documentation), but then he says that switch B transmits from pins 1 and 2 and switch A receives on pins 3 and 6 while in the official books of cisco it is written that both transmit and receive respectively on pins 3, 6 and 1, 2. What is the right version?

[Deepak Kumar · Accepted solution]

Hi, 

I think you misunderstanding the crosstalk method.

here I will explain:

The device A will receive the Packets on ports 1 and 2 (RX) and transmitting on Pins 3 & 6 (TX).

The Device B will also receive the Packets on ports 1 and 2 (RX) and transmitting on Pins 3 & 6 (TX) but at the other end of the cable. Where Pin 1 & 2 has been swapped with 3 & 6.

Device A at the Connector A side and Device B is at Connector B side.

[PietroPoliseno27977]

I got confused looking at the figure at the bottom of this page where the automatic functionality that detects if the cable is correct or not is used. https://www.quora.com/What-is-an-Ethernet-crossover-cable-When-are-they-used In fact, use nic mdi. in this case the switch detects the wrong cable and transmits on pins 1 and 2. Anyway to conclude the crossover logic is 3 and 6 transmits and 1 and 2 receives. stop right? thanks for your intervention