Why would one need to mess with the duplex setting at all? Mine default to full duplex without have to change anything. I did try playing with option 27, but it reverted to full duplex regardless of the settings (0, 1, or 2).
obi202 - port 2 (physical port 3)

obi200 - port 2 (physical port 3), port 3 is a pc in sleep mode
