I see a number of 3700s running 12.2(33)SXH3 that all report 100M unknown-duplex. There appears to be no one-MIB-fits-all for determining duplexity. I wonder if this symptom is an IOS bug or lack of software in Campus Manager 5.1.1.
Does not compute. 3750 switches cannot run 12.2(33)SXH3 code. However, there is no one-MIB-fits-all for duplex. Some devices support the CISCO-STACK-MIB, and some support the ETHERLIKE-MIB.
A duplex type of unknown will be returned if a STACK-MIB supporting device returns auto(4) for portDuplex. This is admittedly a bug.