Uplink with straight through or Cross over

Unanswered Question
Jun 11th, 2009

I am trying to uplink and form a etherchannel between the 3750 regular ports and 3548 regular ports. Could you please any one advise which cable I should be using ?

Note:When I was trying to uplnk 2960 to 3750, it worked with straight through.

I have this problem too.
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Jon Marshall Thu, 06/11/2009 - 06:30

Switch to switch traditionally meant you needed a cross over cable. Nowadays the switches can auto sense the cable and compensate so that's why your 2960 to 3750 worked.

However the 3548 is a considerably older switch and i don't think it supports auto mdix. So go with a cross over cable.


Joseph W. Doherty Thu, 06/11/2009 - 06:35

As Jon notes, newer switches often support auto mdix and should work with either cable type. Don't believe you need an auto mdix device on both sides of a link for it to work. I recall(?) on 3750, though, if "auto" isn't configured for speed/duplex, auto mdix isn't enabled.

glen.grant Thu, 06/11/2009 - 08:40

Joe is correct 3750 supports mdix and you can use either cable "as long as the speed/duplex on the 3750" is set as auto , obviously you want the other end as auto also .

rock48567 Thu, 06/11/2009 - 10:25

Thanks for your reply.

Why I asked this question because the uplink from 2960 to 3750 with Cross over cable in the etherchannel group does not work. I dont know why. It only works perfectly with Straight cables. I am going to test 3550/3548 to 3750. Hopefully it should work with cross cables.

Leo Laohoo Thu, 06/11/2009 - 15:35

Traditionally, you should use Cross-Over cable. But since MDI/MDIX is cheaper by the ton, the 3750 is MDI/MDIX capable.


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