MIB: ZYXEL-PORT-MIB
Select The speed and the duplex mode of the Ethernet connection on this port. Selecting Auto 
(auto-negotiation) allows one port to negotiate with a peer port automatically to obtain the 
connection speed and duplex mode that both ends support. When auto-negotiation is turned on, 
a port on the Switch negotiates with the peer automatically to determine the connection speed 
and duplex mode. If the peer port does not support auto-negotiation or turns off this feature, 
the Switch determines the connection speed by detecting the signal on the cable and using half 
duplex mode. Thus requiring you to make sure that the settings of the peer port are the same in 
order to connect.