This article was written based on the ns5gt. By default all interfaces are set to auto negotiate.

Show Duplex

ns5gt-> get interface trust port phy
Port 1:  link is up, 100 Mbps, auto negotiated to full duplex
Port 2:  link is up, 100 Mbps, auto negotiated to full duplex
Port 3:  link is up, 100 Mbps, auto negotiated to full duplex
Port 4:  link is down, 10 Mbps, forced to half duplex

Change Duplex

ns5gt-> set interface trust phy full 100mb

Changing Duplex back to Auto-negotiate

ns5gt-> unset interface trust phy full 100mb

It is important to notice the way in which we change the interface back to auto negotiate. Setting the port to auto will not work. You will need to unset the current duplex setting instead, to allow for it to default back auto negotiate.