This variable defines whether this interface operates in locked
or unlocked mode. It is locked in each of the following two cases:
1) if swLockAdminStatus is set to locked
2) no IP/IPX interface is defined over this interface and no
VLAN contains this interface.
In unlocked mode the device learns all MAC addresses from this port and
forwards all frames arrived at this port. In locked mode no new MAC
addresses are learned and only frames with known source MAC
addresses are forwarded.