[rrd-developers] Re: RRDtool bug ?

Mike Jackson mhjack at tscnet.com
Mon Aug 5 20:40:16 MEST 2002

On Mon, 2002-08-05 at 09:17, J. Nick Koston wrote:
>   I'm noticing that when using mrtg+rrdtool that any traffic over ~ 125
> megabits seems to be incorrectly saved.  The graph will function fine
> during times when there is less then 125 megabits worth of traffic,
> however as soon as it goes above ~ 125 the graph says that there is
> about ~30-40~ megabits of traffic (verified against sh int counters).
> -Nick  

	I believe that you are seeing double counter wrap.  You need to either:

	1. Use 64 bit counters instead of 32 bit, or
	2. Increase your sample rate from say 5 minutes to 1 minute.

	Whenever I tried to use 64 bit counters on a Cisco, I would get strange
spikes when the counters wrapped, so I ended up using a 1 min sample
interval.  This may have been fixed in newer IOS, I did open a ticket
with Cisco at one time...

	This is a function of the counters that you are using, not MRTG or
RRDTool.  I can't tell you how to change the sample interval in MRTG, as
I wrote my own perl based collection system before MRTG went to using

Mike Jackson <mhjack at tscnet.com>

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