Re: Strange error in test program...

On 08/04/2008, Kris van Rens <krisvanrens.list@gmail.com> wrote:
> > But how do you know which ifIndex.{x} values to ask for?
> > The {x} there is the same as the {x} in the ifPhysAddress.{x}
> > OID. So this is just moving the problem (unnecessarily).
>
>
> I suspected that for IF-MIB::ifIndex{x} = {y} the value {x} would be
> in a strict consecutive order, that is, for your example this would
> give:
>
> IF-MIB::ifIndex.0 = 2
> IF-MIB::ifIndex.1 = 3
> IF-MIB::ifIndex.2 = 27

Nope.
The ifIndex value is exacly the same as the index subidentifier.
So this walk would actually read:

IF-MIB::ifIndex.2 = 2
IF-MIB::ifIndex.3 = 3
IF-MIB::ifIndex.27 = 27


That's why modern MIBs mark the index object as "not-accessible".
It doesn't provide any useful information. These index values can
be retrieved from walking any of the other columns instead.



> So I would iterate three times (from IF-MIB::ifNumber.0) and build an
> index list with which I can build the 'IF-MIB::ifPhysAddress.{y}'
> strings.
>
> Very tedious, I know, but it works for SNMP v1, for which I must most
> likely build in compatability.

If you need SNMPv1 support, then the answer is to use GETNEXT:

GETNEXT ifPhysAddress
(gives back the value for ifPhysAddress.2)
GETNEXT ifPhysAddress.2
(gives back the value for ifPhysAddress.3)
GETNEXT ifPhysAddress.3
(gives back the value for ifPhysAddress.27)
GETNEXT ifPhysAddress.27
(gives back the value for ifAdminStatus.2
which isn't relevant, so you can stop)

Walking off the end of the column means you don't actually
need to retrieve ifNumber.0

Dave

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