The state of this NBP entry.
Setting this object to the value invalid(2) has
the effect of invalidating the corresponding
entry in the nbpTable. That is, it effectively
disassociates the mapping identified with said
entry. It is an implementation-specific matter
as to whether the agent removes an invalidated
entry from the table.
Accordingly, management stations must be
prepared to receive from agents tabular
information corresponding to entries not
currently in use. Proper interpretation of
such entries requires examination of the
relevant nbpState object.