The protocol migration control on this port. When the
object value of stpxSpanningTreeType is mst(4) or
rapidPvstPlus(5), setting true(1) to this object forces
the device to try using version 2 BPDUs on this port.
When the object value of stpxSpanningTreeType is neither
mst(4) nor rapidPvstPlus(5), setting true(1) to
this object has no effect. Setting false(2) to this
object has no effect. This object always returns
false(2) when read.