The enabled/disabled status of the Spanning Tree topology
change notification.
When this object is set to enabled(1) topology change
notifications SHOULD be generated by the agent.
When this object is set to disabled(2) topology change
notifications MUST NOT be generated by the agent.
When this object is set to edgePortDisabled(3) topology
change notifications MUST NOT be generated by the agent
for ports that are operating as edge ports, as specified
by dot1dStpPortOperEdgePort, and SHOULD be generated for
all other applicable ports.