duplex mismatch

Unanswered Question
Dec 10th, 2008


I am getting log in cisco router for sub-interface- duplex mismatch discovered on GigabitEthernet0/1.2 (not half duplex), with SEP00170EF9E8B6 Port 1 (half duplex).

I must have to set duplex and speed auto in interface gi0/1 for other VLAN.

How to solve this.

Plz, help.



I have this problem too.
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Giuseppe Larosa Wed, 12/10/2008 - 23:46

hello Tarun,

these messages usually are CDP derived.

Another thought is that speed and duplex are physical properties that can be configured only on the physical interface gi0/1.

So a complain for duplex mismatch is a true issue only if it is seen in

sh int gi0/1.

Then the IP phone should be the first device out the port.

In this case you should change the cable or verify cabling it can be a cable issue

or access via web the ip phone page and check for collisions errors or other signs that is putting the link in half duplex.

Hope to help



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