[mrtg-developers] Mathematical operations on OIDs

S Shipway s.shipway at auckland.ac.nz
Sat Oct 24 05:48:07 CEST 2009

If one of the countes wraps, then MRTG should be able to detect it.  The only problem would be if two counters wrap during the same polling cycle, which may confuse things.

If you don't want the negative numbers, then no trouble - by default, since they are outside the defined range (0-maxbytes) they will be dropped.  It's if you want to keep them that you need to tune the RRD files.


Thanks for the response. But my graph needs to have only the positive values and not negative values.
The negative values are caused because the oid3 - (oid4 * 10) calculation returns a negative value.
In my case when oid3 - (oid4 * 10) is a negative value (not always though), how can i handle them in mrtg?

And another query is what will happen if the 4 counters (oid1 to oid4) overflow?
For example, the oid4 counter resets at a slower rate than the oid3 counter. There are chances of getting a spike on the graph when oid3 value is very high and oid4 value is negligible and
oid3 - (oid4 * 10) is approx equal to oid3.
how can we handle this scenario?

View this message in context: http://n2.nabble.com/Mathematical-operations-on-OIDs-tp3524231p3882569.html
Sent from the MRTG Developers Mailinglist mailing list archive at Nabble.com.

More information about the mrtg-developers mailing list