[ECOS] Re: SNMP lockup

Grant Edwards grante@visi.com
Sat May 9 09:47:00 GMT 2009

On 2009-05-09, Sergei Gavrikov <sergei.gavrikov@gmail.com> wrote:

> [snip]
>> What I'd like a pointer on is the interface numbering in SNMP
>> OIDs.  Are the interfaces supposed to be numbered 1..N with
>> interface 0 being non-existent?  Or are eCos interface numbers
>> off by one and they should really be 0,1 instead of 1,2? [I
>> tried looking through the OID/ASN.1 docs, but got lost rather
>> quickly.]


>> I looked at network traces for one customer site using, I
>> believe, HP Insight. It does read the interface attributes for
>> interfaces 1 and 2.  I don't see it attempt to read attributes
>> for interface 3 (which doesn't exist). I do see it attempt to
>> read attributes for interface 0 (which also doesn't exist).
>> If interface numbers are supposed to start at #0, will
>> renumbering the interfaces at this point (after product has
>> been shipping for 7 years) cause more problems that it will
>> solve?
> That's known SNMP "issue"

What is a known issue?

> -- ?get? might want that the OID ends in .0
> Example:
> snmpget -c public -O X -v2c bridge.local sysDescr
> SNMPv2-MIB::sysDescr = No Such Instance currently exists at this OID
> snmpget -c public -O X -v2c bridge.local sysDescr.0
> SNMPv2-MIB::sysDescr.0 = STRING: Foo bar baz

I'm afraid I don't understand your point.

> So, IMHO, it's better to fix the agent than to make managers
> work "properly".

I wasn't propsoing that we not fix the agent.  What I was
asking was

 * Which of two fixes is the "standards-correct" one:

    1) Leave the interfaces numbered 1,2 and fix handling
       for queries of interface <1.

    2) Change the interface numbers to 0,1.

 * If 2) is what the standards specify, are we still better off
   with 1) to maintain some backwards-compatiblity with older

My posted fix that implements choice 1).

I misunderstanding OID sematics? 

Is supposed to refer to the physical
address of the first network interface?

Or is the physical address of the first
interface and <...>.0 is something fundamentally different?


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