[mrtg] totals do not add up when graphing multiple targets

[McDonald, Dan]

On Wed, 2009-02-11 at 05:19 -0800, pvh wrote:
> Hello,
> 
> I've recently had to install MRTG on Windows with the latest ActivePerl at
> work to monitor a server.
> What I'm doing is graphing all active interfaces (as per the default
> cfgmaker configuration), and I added a totals graph which is simply
> something like that:
> 1:community at ip + 2:community at ip + 3:community at ip .. 

So, when one counter rolls over, mrtg has no way of knowing (and
correcting)

> I'm working with fast ethernet interfaces (all 32 bit counters) here.

Thus rollovers are frequent.

The only way to accurately do this is to collect the three counters
separately, and use routers2.cgi (or some other similarly enlightened
front end, but there aren't any others published with this feature) and
build a stacked graph to show the actual total.

Note that that requires RRDtool as a backend

-- 
Daniel J McDonald, CCIE #2495, CISSP #78281, CNX
Austin Energy
http://www.austinenergy.com

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