Cisco IP phones duplex settings changes from auto negotiate to 100 full duplex

[heathersweaters]

There are a number of clients where the duplex settings on their ip phones are set to 100 full duplex instead of the default selection: auto negotiate. I'm sure they did not change it themselves. The IP phone model is CP-9951. What could cause this change?

[Manish Gogna]

Hi,

Do the speed / duplex settings for these phones match the settings on the switchport? There is no way to change the settings on Phone configuration page without logging into cucm. You can collect the tomcat / audit logs to check if someone is logging into cucm admin page to make any changes to the configuration.

HTH

Manish