[mrtg] Different values on graph from MRTG & Cricket

Alex van den Bogaerdt alex at ergens.op.het.net
Tue Nov 6 14:57:01 CET 2007

On Tue, Nov 06, 2007 at 08:53:46AM +0300, Mir Hafeez Ali wrote:
> Hi All,
> There is a difference in values of the traffic on either side of the link.
> While I am polling the graphs with MRTG, our ISP has Cricket.  I always see
> a difference of around 2% of total traffic. 

> For an example if I am seeing the peak value of 1996K from my graph polling
> on my router interface, the ISP graph shows around 2048K which is polling on
> the interface on their side.

Could be several things, perhaps a combination.
- protocol overhead
- rounding (truncating) errors
- wrong "kilo" setting

> Please if I can know why this behavior happening on the link.  Both ends are
> having Cisco Routers and are connected through ATM link.  This is very
> important as we are always claiming our bandwidth not getting as committed
> by the ISP.

First things first: make sure you are measuring the same counter.
Extreme example: if one end is measuring "on the wire bits", and the
other is measuring "payload data", the numbers won't be the same.
And make sure you have 1000 (not 1024) for kilo.


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