ifIndex

Sat Oct 13 12:45:29 UTC 2018

Saku,

The issue isn't that ifindexes change during operation. That would truly make SNMP useless. The issue is that they change across reboots. That's where features such as Cisco's Interface Index Persistence helps out. 

-mel via cell

> On Oct 13, 2018, at 2:59 AM, Saku Ytti <saku at ytti.fi> wrote:
> 
>> On Fri, 12 Oct 2018 at 21:40, Chris Adams <cma at cmadams.net> wrote:
>> 
>> Is there any good excuse that SNMP client software can't handle a basic
>> design of SNMP - indexed tables?  ifIndex is far from the only index in
>> SNMP, and many of them still change today at various times.
>> 
>> It isn't that hard to fetch the indexed field in a bulk get, rewalking
>> the table if you don't get what you expected.  Cricket did this in 1999.
> 
> It's never going to be provably correct, depending on what stability means.
> 
> You fetch relation at t0, then at t1 you fetch data. Was the relation
> same at t0 and t1? You can gain some confidence by fetching relation
> again at t2 and disregard data if t0 != t2. But this becomes polling
> expensive quite fast, and still not provably correct. This may be
> nitpicking, but I've always felt uneasy about the lack of guarantee.
> 
> I wonder if those who have stable indeces, have them for all cases,
> all logical interfaces and virtual interfaces?
> 
> -- 
>  ++ytti