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TOPIC: Auto MDIX Switching

Auto MDIX Switching 10 years 1 month ago #16381

  • TheBishop
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I was doing some tests recently with a hardware encryption unit connected to a Cisco switch by an RJ45 patch lead. Strictly speaking this should have been a crossover lead but I didn't have one to hand and was pleasantly surprised to plug in a straight-through lead and find it worked, thanks to auto MDIX switching on the encryptor. However careful tests showed that the throughput was noticably better with the correct lead, the implication being that auto MDIX switching might be convenient but introduces some overhead.
Anyone else experienced this?
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Re: Auto MDIX Switching 10 years 1 month ago #16387

  • Dove
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Hi,
I also tried like this that I am using Catlyst 2950 switches. Basicall to interconnect two switch we need to use Crossover cable right? but I interconnected both the switches with straight through cable, now I can access the resource from accross the switches.

I am wondering how it works!!! can anyone explain me how its working? and then why Cisco suggest to use Crossover cable..?


Rgds
Dove.

Dove
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Re: Auto MDIX Switching 10 years 1 month ago #16395

  • d_jabsd
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Auto-MDIX was put in to make life easier and came from the consumer market, where the average user is not knowledgeable enough to know the difference.

It works by detecting the voltage differential caused by the signal, and crosses the cable over at the port.

You will see a performance decrease if the wrong cable is used, as the ports default to straight-through and will only crossover when signal is detected on the wrong pairs. It is my understanding that if you unplug the cable, the port will immidiately switch back to straight-through, leading my to believe that it is continuously checking for MDIX changes, which will decrease your throughput.

IMO, this feature has no business being included in higher caliber devices. Since I make my own cables, crimping up a crossover only takes a minute, so i usually turn Auto-MDIX completely off.

IIRC, the command is 'no mdix auto'. Since the range command has been added as well, its pretty simple to turn it off across the entire device.
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Re: Auto MDIX Switching 10 years 1 month ago #16399

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Thought as much. Thanks d_jabsd
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Re: Auto MDIX Switching 10 years 4 weeks ago #16439

  • Dove
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Thanks

Rgds,
Dove

Dove
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