Configure the duplex mode on the Ethernet module. This command applies to 10/100/1000 Mb/s ports.
default duplex
default duplex port {slot/port[/sub-port][-slot/port[/sub-port]][,...]}
duplex { half | full }
duplex port {slot/port[/sub-port][-slot/port[/sub-port]][,...]}
Identifies the slot and port in one of the following formats: a single slot and port (slot/port), a range of slots and ports (slot/port-slot/port), or a series of slots and ports (slot/port,slot/port,slot/port). If the platform supports channelization and the port is channelized, you must also specify the sub-port in the format slot/port/sub-port.
The default is half.
GigabitEthernet Interface Configuration