GVRP registration information
normal: This is the default configuration. Allow create, register
and unregister vlans dynamiclly at this port.
fixed: Aallow create and register vlan manually at this port.
Prevent from unregistering vlans or registering known
vlans of this port at another trunk port.
forbidden: Unregister all vlans but vlan 1, forbid to create or
register any other vlans at this port.