This attribute specifies whether the port secure feature is enabled. The
secure feature, if enabled causes the following things to happen:
a) disallows dynamic learning,
b) disallows frames to be forwarded that do not satisfy the following
condition: the mac address of the source should be found in the
forwarding table and the destination mac address of the frame should
also be found in the forwarding table. In addition to this, the port the
frame was received on should figure as the in port, given the destination
mac address found in the frame.
c) disallows frames to be forwarded if the allowed to go port map for the
destination mac address is empty.
This feature in effect allows the user to choose the hosts that can
generate traffic and the hosts that can receive traffic through this bridge
unit.