[mrtg] Re: interface removal cause snmpwalk

McDonald, Dan Dan.McDonald at austinenergy.com
Mon Jun 19 21:29:23 MEST 2006

On Mon, 2006-06-19 at 12:02 -0400, Mark Jones wrote:
> I am accessing the interfaces by name not if num

Right, so whenever the cached ifnum doesn't match the ifname, it has to
walk the whole ifName table to figure out where it is supposed to be...

The only ways around that behavior are to re-run cfgmaker whenever you
make a config change, before mrtg runs; or to use ifnum rather than
ifname as the ifref.

I'm fairly certain that if you use snmp v2, (or v3) that the snmpwalk
built into SNMP_Utils.pm switches to bulk getnext's rather than just
getnext, so an snmpwalk should be less onerous with snmp v2 than with

A long term solution would be to request that Cisco make the ifMib
context aware, and then create five or six separate contexts, and run a
separate mrtg instance per context.  That way, mrtg would only be
running snmpwalk over 1/6th of the interfaces at a time.  Unfortunately,
Cisco doesn't support Contexts for that purpose at this time.

Daniel J McDonald, CCIE #2495, CNX, CISSP #78281
Austin Energy

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