[mrtg] Re: graphing max?

Eric Brander Eric_Mailing_List at rednarb.com
Mon Oct 25 21:42:35 MEST 2004

Mohamed S. wrote:
> Hi!
> I have the following config to retrieve bandwidth info from a CISCO switch:
> cfgmaker  --ifdesc=name --no-down \
> --global "Interval: 5" --global "Refresh: 300" \
> --global "Options[_]: growright, avgpeak, bits, noinfo, integer" \
> --global "MaxBytes[_]: 125000000" \
> --global "AbsMax[_]: 125000000"
> The Max settings of 125000000 should allow me to graph well over 100Mbit/s
> (125000000*8), actually 1Gbit/s worth of traffic since this is on a fiber
> optic GigE port. Despite the MaxBytes and AbsMax settings however, when the
> BW graph climbs to over ~105Mbit/s, it falls back down to 0! and then
> continues to climb from there. ie: if port is actually pushing 140Mbit/s, it
> will only show ~35Mbit/s on the graph after having dropped down to 0.
> I'm not sure what is going on here. Any clues?

Counter wrap.  If you're using 32-bit counters, they are wrapping during 
the 5-minute polling interval.

If that's the case, you'll need to use the 64-bit counters instead or go 
to 1-minute polling interval.

For more help on this subject, search the archive for 64-bit or 1-minute 


Eric Brander

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