Indicates the operational status of the port for the
MST protocol.
edge -- this port is an edge port for the MST region.
boundary -- this port is a boundary port for the
MST region.
pvst -- this port is connected to a PVST/PVST+ bridge.
stp -- this port is connected to a Single Spanning
Tree bridge.
dispute -- this port, as a designated port, received an
inferior BPDU with a designated role and the
learning bit being set.