As you all know, the ports in the 3550s comes with DTP enabled. I have gone through the messages posted in this group in last Nov. 23rd. The recommended solution to configure the port to "switchport nonegotiate" didn't work. I do get the message "Command rejected: Conflict between 'nonegotiate' and 'dynamic' status"
Please see the initial config. and the response to the command"-
switchport access vlan 20
switchport mode dynamic desirable
Enter configuration commands, one per line. End with CNTL/Z.
Command rejected: Conflict between 'nonegotiate' and 'dynamic' status.