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Changing nic settings on Pres Server

Answered Question
Jan 6th, 2010
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Hello I am getting a CDP duplex miss match error on my core switch from one of my UC Presentation servers and I would like to enable auto negotiation.  The current settings of the server is 100 full but the switch is set to auto ( I would like to get a gig). From a ssh shell I can issue the command:

set network nic eth0 auto en

I get a warning that I will lose connectivity but it still comes back at auto disabled.

Am I missing a parameter?

Thank you,


Correct Answer by Tommer Catlin about 7 years 7 months ago

here is the bug:


as long as you set both to match, you should be fine.  Just turn off CDP for that port and ignore the warnings.

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Overall Rating: 3.7 (3 ratings)
htluo Thu, 01/07/2010 - 05:54
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The "duplex mismatch" is a false alarm.  You'll find it on certain version of CUCM, CUPS, CER.  Just turn off CDP on that specific port.



Michael Murray Thu, 01/07/2010 - 07:44
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Your set network nic command looks correct. Not sure why it's not taking.

If your CUP server is set to 100/full and the switch is auto/auto then you'll get a duplex mismatch. Autonegotiation is a passive process and while passively detecting speed is easy, detecting duplex is not. So the auto side will configure to 100/half (half duplex being the default), thus your mismatch.

You'll need to either set both sides to 100/full or auto/auto. I would recommend hard coding both sides to 100/full instead of auto/auto.


John Palmason Thu, 01/07/2010 - 09:51
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Thank you, I know this sounds like a basic problem but I wasn't getting the expected behavior.  I have solved this problem and CDP is now happy on the core switch.  Thank you all for taking the time to respond.



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