Re: Problem with mib successor on mib-II objects

Juergen Schoenwaelder (schoenw@cs.utwente.nl)
Thu, 3 Oct 1996 20:51:09 +0200

michele@pqtech.com (Michele Chen) said:

Michele> Here's another problem I'm having with scotty that
Michele> changed between 2.0.2 and 2.1.3. When I do a 'mib
Michele> successor system' under 2.0.2, I get the rfc1213
Michele> objects I expect: "sysDescr sysObjectID sysUpTime
Michele> sysContact sysName sysLocation sysServices".

Michele> But with 2.1.3, rather than the rfc1213 objects, I get
Michele> the rfc1907 v2 mib objects: "sysDescr sysObjectID
Michele> sysUpTime sysContact sysName sysLocation sysServices
Michele> sysORLastChange sysORTable". I thought I could
Michele> explicitly get the rfc1213 objects by calling 'mib
Michele> successor RFC1213-MIB!snmp', but it returns 'no object
Michele> "RFC1213-MIB!snmp"'.

The mib(n) man page says:

The mib successor command returns a list of all known
successors of the MIB node identified by label.

Your script should never make any assumptions about the set of known
successors of a MIB node since this set depends on the set of loaded
MIB modules. You did not discover a change in the Tnm extension but a
change in the set of MIB objects defined in IETF standard MIBs.

The mib(n) man page says about MIB node names:

A globally unique name is therefore the combination of the MIB
module name and the name of a MIB node defined in the module (e.g.
SNMPv2-MIB!sysDescr).

The only purpose of the SNMPv2-MIB!sysDescr notation is to make the
descriptor sysDescr unique. You are trying to use this notation as a
filter mechanism which of course does not work. (Note, the Tnm
extension does not keep information about multiply defined nodes
because the SMI forbids all semantic changes to a MIB node once it is
has been defined.)

One solution to your problem is to remove rfc1907.mib from the list of
default MIB modules in $tnm(mibs:core) during startup. But anyway, if
you know that you are only interested in a subset of elements, why
don't you simply list this subset in your script?

Juergen

--
Juergen Schoenwaelder schoenw@cs.utwente.nl http://www.cs.utwente.nl/~schoenw
Computer Science Department, University of Twente,   (Fax: +31-53-489-3247)
P.O. Box 217, NL-7500 AE Enschede, The Netherlands.  (Tel. +31-53-489-3678)