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Streight/Crossover cable

Why was the decision made to let PCs/routers/APs transmit on pin 1 and 2, and hubs/switches on pin 3 and 6?. If all devices transmit on the same pins, we could just always use crossover cables. The would also be no need for Auto-MDIX. Wouldn't that make life easier?

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Hall of Fame Community Legend

Streight/Crossover cable

The would also be no need for Auto-MDIX. Wouldn't that make life easier?

Are you saying that disable MDI/MDI-X would make life easier?  I disagree.  MDI/MDI-X certainly makes things alot easier and I've been enjoying this feature since it was first rolled out with the 3750!

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Streight/Crossover cable

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Streight/Crossover cable

Why was the decision made to let PCs/routers/APs transmit on pin 1 and 2, and hubs/switches on pin 3 and 6?. If all devices transmit on the same pins, we could just always use crossover cables. The would also be no need for Auto-MDIX. Wouldn't that make life easier?

A medium dependent interface (MDI) describes the interface (both physical and electrical) in a computer network from a physical layer implementation to the physical medium used to carry the transmission. Ethernet over twisted pair also defines a medium dependent interface crossover (MDIX) interface.

The X refers to the fact that transmit wires on an MDI device must be connected to receive wires on an MDIX device. Straight through cables connect pins 1 and 2 (transmit) on an MDI device to pins 1 and 2 (receive) on an MDIX device. Similarly pins 3 and 6 are receive on an MDI device and transmit on an MDIX device.

The general convention was for network hubs and switches to use the MDIX configuration, while all other nodes such as personal computers, workstations, servers and routers used an MDI interface.

Hope to Help !!

Ganeshh Iyer

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Streight/Crossover cable

Sure, but if we would only have MDIX we could always use crossover cables. Right?

MDIXMDIXMDIXMDIXMDIX

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Hall of Fame Community Legend

Streight/Crossover cable

Sure, but if we would only have MDIX we could always use crossover cables. Right?

Sure you can.  As long as you have one in handy whenever you need it.

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VIP Expert

Streight/Crossover cable

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The    Author of this posting offers the information contained within this    posting without consideration and with the reader's understanding that    there's no implied or expressed suitability or fitness for any  purpose.   Information provided is for informational purposes only and  should not   be construed as rendering professional advice of any kind.  Usage of  this  posting's information is solely at reader's own risk.

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Pieter Verberne wrote:

Sure, but if we would only have MDIX we could always use crossover cables. Right?

MDIXMDIXMDIXMDIXMDIX

Yes and it would also be true if all devices had MDI.

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Streight/Crossover cable

Uhm, yes right :-)

But there has to be a reason why both MDI and MDIX are both in use. What could be the reason? What is the advantage of using both MDI and MDIX.

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VIP Expert

Streight/Crossover cable

Disclaimer

The     Author of this posting offers the information contained within this     posting without consideration and with the reader's understanding  that    there's no implied or expressed suitability or fitness for any   purpose.   Information provided is for informational purposes only and   should not   be construed as rendering professional advice of any kind.   Usage of  this  posting's information is solely at reader's own risk.

Liability Disclaimer

In     no event shall Author be liable for any damages whatsoever   (including,   without limitation, damages for loss of use, data or   profit) arising  out  of the use or inability to use the posting's   information even if  Author  has been advised of the possibility of  such  damage.

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But there has to be a reason why both MDI and MDIX are both in use. What could be the reason? What is the advantage of using both MDI and MDIX.

That's a good question!  MDI to MDIX allows use of of a straight through cable.  I'm unaware of any technical reason why such a cable would be better than a crossover cable, but perhaps there is on.

Otherwise, it might just be something like that just how it has been done for other communication cables that are logically DTE/DCE where their ports swap pins too.

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Streight/Crossover cable

What is the advantage of using both MDI and MDIX.

It minimizes engineers paying money into the "swear jar" when they go "Where the is that cross-over cable, you ."

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