The SYNTAX of ieee8021MstpPortPathCost is Integer32 (1..200000000).
Other path cost writable objects can get the value 0, to denote the
automatically calculated default cost value.
Table 17-10 (Clause 17.2.6) refers ieee8021MstpPortPathCost to 13.27.25,
while its MIB description refers it to 13.27.33. The MIB description
seems to be correct, since the table is indexed by both port and MST
instance, and there is one InternalPortPathCost (17.27.33) per port for
each MSTI.
17.27.25 seems to be covered by ieee8021MstpCistPortAdminPathCost.