[mrtg] Bandwidth of entire Switch

Daniel J McDonald dan.mcdonald at austinenergy.com
Wed May 7 14:20:22 CEST 2008

On Wed, 2008-05-07 at 07:59 -0400, scoob8000 wrote:
> Why couldn't he just do something like:
> Target[totalswitch]: 1:public at + 2:public at +
> 3:public at + 4:public at
> For all the ports he wants to graph?  (And set maxbytes accordingly)

Because the cumulative rollover effect gives vastly unpredictable
results.  MRTG can cope with a single counter rollover.  Trying to sum
52 gigabit interfaces and make sense of the rollovers is sheer madness.
Even two interfaces is problematic, and will result in un-predictable
spikes and valleys.

> Or you could use a shell script (linux) to minimize your queries.
> Query all the ports for your individual charts, then add them together
> for a aggregate chart..

Why not just use routers2?  Or ignore the whole request because it
sounds like a PHB wants it (who cares how busy the switch fabric is if
it is not a constrained resource?  It's not like knowing the aggregate
traffic is going to enable you to plan/justify when a switch upgrade is

Daniel J McDonald, CCIE #2495, CISSP #78281, CNX
Austin Energy

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