I experienced this duplex mismatch problem using ESXi and cucm 7.0.2. The problem only happened with the Pub showing up as half duplex at the switch, no matter what I set it to. The Pub cli "show network eth0" showed 100/full no matter what.
Finally, I shut the CUCM down. Went to the VMware settings for the Pub and deleted the existing NIC. I reinstalled an E1000 NIC. When I restarted the Pub, it was connected at 1000/full, which is what I wanted. It's possible reinstalling the flex NIC type may also work.
Message was edited by: shockinac
CDP needs to be disabled on the interface generating the error. What happens is ESXi is running the native switch of OS causing these errors. IE: (%CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on FastEthernet0/0 (not full duplex)
To fix this little issue run the following on the interface in question.
"NO CDP ENABLE" for newer IOS versions "NO CDP ADVERRTISE-V2