Cisco Systems Interlinking switches / port speeds

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Subject Author Date
Interlinking switches / port speeds thefunnel@aol.com 07-12-07
Posted by thefunnel@aol.com on July 12, 2007, 12:09 pm
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Hi,

I am having difficulties connecting two switches (3750s) together via
copper (using auto mdix). I was always under the impression ports
should either be set to fixed speeds or set to auto at both ends. You
should not have a combination of fixed / auto or mismatches can occur.
I seem to be seeing the opposite:


"speed 10" to "speed 10" = NOT WORKING
"speed 100" to "speed 100" = NOT WORKING

But if only one end is set to a fixed speed:

"speed 10" to "speed auto" = WORKING
"speed 100" to speed auto" = WORKING

I have also tried setting both ends to full and half duplex - still
nothing. Would someone mind explaining why this is happening? I can
achieve the desired effect by only configuring the speed on one end
but I thought Cisco avoid against this?

Thanks,

Paul


Posted by on July 12, 2007, 12:37 pm
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> Hi,
>
> I am having difficulties connecting two switches (3750s) together via
> copper (using auto mdix). I was always under the impression ports
^^^^^^^^^^^^^^^
> should either be set to fixed speeds or set to auto at both ends. You
> should not have a combination of fixed / auto or mismatches can occur.
> I seem to be seeing the opposite:
>
>
> "speed 10" to "speed 10" = NOT WORKING
> "speed 100" to "speed 100" = NOT WORKING

Auto mdix requires autonegotiate.

> But if only one end is set to a fixed speed:
>
> "speed 10" to "speed auto" = WORKING
> "speed 100" to speed auto" = WORKING

If one end is auto, that end will do the auto-mdix.

> I have also tried setting both ends to full and half duplex - still
> nothing. Would someone mind explaining why this is happening? I can
> achieve the desired effect by only configuring the speed on one end
> but I thought Cisco avoid against this?

I don't see that you've tried "speed auto" to "speed auto".
That's the setting that I would recommend.

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