When you use "mls qos trust device cisco-phone" command in switch interface, will it effectively perform two functions:
1. Trust COS settings coming from the Phone and perform cos-dscp mapping accordingly (based on COS=5) or do you additionally need "mls qos trust cos" command?
2. Untrust DSCP coming from Pc connected to the back of IP Phone like if "switchport priority extend cos 0" command was also entered (when it is not)?
So in summary when you enter both commands:
mls qos trust device cisco-phone
mls qos trust cos
are you effectively trusting COS only when IP Phone is connected and not trusting it otherwise and also when IP Phone IS connected you still set COS=0/DSCP=0 for PC traffic?