Hi Simon,
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? Regards, Nisha Westlake, Simon wrote: > > Nisha, > > For reference, this is the script I use in order to tune my files (I graph > cable modem signal levels and I have to tune all the files to allow them > to display negative dB values) > > for RRD in `ls /var/www/mrtg/*/*-down.rrd` ; do rrdtool tune $RRD -i > ds0:-60 -a ds0:60 blah ; done > > You will obviously have to modify the values to match your setup.. > > HTH > > -- > Simon Westlake > > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of S Shipway > Sent: Wednesday, October 21, 2009 5:29 PM > To: [email protected] > Subject: Re: [mrtg-developers] Mathematical operations on OIDs > > > MRTG is able to handle negative values, provided that: > a) you are using RRDTool as your backend, not native mode, and > b) You manually set the Minimum for the DS appropriately within the > RRD file using RRDTune (MRTG always sets the minimum to 0). > > Also, unless this is a gauge, you might need to use 'derive' rather than > 'counter' in order to cope with negative slopes. > > Steve > > ________________________________ > From: nisha [via MRTG Mailinglists] > [mailto:[email protected]] > Sent: Wednesday, 21 October 2009 11:04 p.m. > To: Steve Shipway > Subject: RE: [mrtg-developers] Mathematical operations on OIDs > > Hi Steve, > > This solution worked. But now i have a problem when the calcualtion > results in a negative value. > > Lets say [oid1 - (oid2 * 5)] gives a positive value and [oid3 - (oid4 * > 10)] gives a negative value then the rrds are not able to update these > values and hence my graph shows Nan > > Have you come across something like this before? Can mrtg can handle this? > > Regards, > Nisha > > S Shipway wrote: > This is not possible as you state it; Target line calculations can only be > done on an OID pair. However you might achieve it like this: > > Target[targetname]: oid1&oid3:co...@host - ( oid2&oid4:c...@host * 5 + ( > pseudoZero&oid4:co...@host * 5 ) ) > > Note that the spaces around the brackets and arithmetic signs are > essential. 'pseudoZero' is a magic MRTG virtualOID that always resolves > to zero. > > Check the documentation on complex calculated Target lines online at > www.mrtg.org<http://www.mrtg.org/> or get a copy of the book from > www.steveshipway.org/book<http://www.steveshipway.org/book> > > Your example below is using oid4x10 in one place but oid4x8 in another but > I guess that's just a typo. > > Steve > > ________________________________ > From: nisha (via Nabble) [mailto:[email protected]] > Sent: Thursday, 27 August 2009 11:02 p.m. > To: Steve Shipway > Subject: [mrtg-developers] Mathematical operations on OIDs > > Hi all, > > I want to perform mathematical operations on OIDs in the target line. For > example, there are 4 oids as shown below: > traffic packet > In oid1 oid2 > Out oid3 oid4 > > > Now i want to apply the following formula > traffic in = oid1 - (oid2 * 5) > traffic out = oid3 - (oid4 * 10) > > My target line in router cfg file is like this: > Target[targetname]: oid1&oid3:c...@hostname - (oid2 * 5)&(oid4 * > 8):c...@hostname > > Is this possible in MRTG? Can the router cfg file handle oids with > mathematical operations? > > ________________________________ > View message @ > http://n2.nabble.com/Mathematical-operations-on-OIDs-tp3524231p3864251.html > To start a new topic under MRTG Developers Mailinglist, email > [email protected] > To unsubscribe from MRTG Developers Mailinglist, click here< (link > removed) =>. > > > -- > View this message in context: > http://n2.nabble.com/Mathematical-operations-on-OIDs-tp3524231p3868979.html > Sent from the MRTG Developers Mailinglist mailing list archive at > Nabble.com. > > _______________________________________________ > mrtg-developers mailing list > [email protected] > https://lists.oetiker.ch/cgi-bin/listinfo/mrtg-developers > This E-mail and any of its attachments may contain Time Warner > Cable proprietary information, which is privileged, confidential, > or subject to copyright belonging to Time Warner Cable. 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