[mrtg] Re: MRTG/spikes after router reboot with fix/patch for 2.9.29

Michael Markstaller mm at elabnet.de
Mon Apr 19 20:15:50 MEST 2004

> I got your message at the right time. I was too looking for a workaround for
> the strange spikes. The problem I face is not due to Router reloads, but
> whenever my MRTG server loses connectivity with the routers, it displays
> spikes.  Hope your patch works based upon router uptime. 
yes, it looks on sysUptime because it's the only save way I can imagine to determine for MRTG if the device reloaded or a counter-wrap probably occured ;)

> Will it work for my case?
Not likely. The problem with the spikes & reloads is described in my inital post

with my patch it looks on the sysUptime, if it's smaller than interval/lastpoll it reports nul to enforce the next recorded value counting from 0.

anyway, if you only loose connectivity to the devices at least this is not the reason for your spikes.
I've also many devices with flapping connectivity (about 3-5 of few hundred per round!) and never got any spikes due to devices being temporary unreachable.
Easiest thing is to enable some debugging and looking on the values mrtg reports to have polled.
make sure your're using rrdtool, have reasonable maxbytes and your devices aren't reporting crap.
IMHO, if you're looking on 100mbit or faster the only real save way to get accurate stats over long timeperiods is using 64-bit counters. I know there're other opinions ;)


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