The same text that follows 'MIB=' in sysDescr, EXCLUDING the 'MIB='. The MIB version is identified by a two-digit major version number (with a leading zero if needed), followed by a lower-case letter minor version and 0 or more character info number. The major MIB version is changed whenever it becomes incompatible to its previous version; i.e., some variables have been deleted or the behavior/meaning has been changed. Minor version number is changed when new features have been added, but existing behavior is completely unchanged.