A reference to MIB definitions specific to the particular
routing protocol which is responsible for this route, as
determined by the value specified in the route's
cIpCidrRouteProto value. If this information is not
present, its value should be set to the OBJECT IDENTIFIER
{ 0 0 }, which is a syntactically valid object identifier,
and any implementation conforming to ASN.1 and the Basic
Encoding Rules must be able to generate and recognize this
value.