[mrtg] Re: Monitoring Gigabit Ethernet ports...

Lars Holmström lars.holmstrom at flysta.net
Sat May 19 10:29:52 MEST 2001



As far as I understand there must be support for 64-bit counters both internally of
the SSR as well as in the MIB. I do have a couple of SSR's in my LAB so on Monday I
will check if they support this. WHat is the version of the SSR image software you
have (system show version) ?
/Lars

Marc Duchesneau wrote:

> Lars,
>
> What is this 64-bit interface you mentionned?  Is this another MIB ?
>
> At 08:35 PM 5/18/2001 +0200, Lars Holmström wrote:
>
> >This has been discussed on this list before.
> >
> >One limitation to keep in mind is that the default configuration file
> >generated
> >by MRTG cannot accurately measure bandwidth above about 114 Mbps (Megabits per
> >second). The reason is that the default interface counter is a 32-bit number,
> >and a 32-bit number will rollover twice in a period of 5 minutes at more than
> >114 Mbps. (232 = 4,294,967,296 bytes, multiplied by 8 (bits in a byte),
> >divided
> >by 300 seconds in 5 minutes, is 114,532,641 bits per second, or roughly 114
> >Mbps.) MRTG or any other SNMP program cannot correctly account for a double
> >rollover. The graph will appear to peak at about 114 Mbps and never go beyond
> >that, when in reality the interface could be running well beyond that rate. To
> >get around this, you must change the configuration file to pole a special
> >64-bit
> >interface counter, or poll MRTG more frequently than 5 minutes.
> >
> >I do not believe the SSR has 64 bit counters.
> >
> >/Lars
> >
> >"Cihan Subasi (Garanti Teknoloji)" wrote:
> >
> > >         Hi,
> > >
> > >         I am trying to monitor Gigabit Ethernet port usage on Cabletron
> > > SSR8000 chassis....Graphs seems ok when traffic is low (10-20 Mbits/s) but
> > > when traffic goes higher than those values graphs becomes flat (my
> > > understanding is because mrtg cannot get a new value from the port
> > keeps the
> > > last one...Anybody every experienced similar things on Gigabit port
> > > monitoring? Thanks
> > >
> > > *****************************************************************
> > > Cihan Subasi
> > > Garanti Technology
> > > Network Services - Project Manager
> > > *       +90 212 478 3426
> > > GSM:    +90 533 2701915
> > > mailto:cihans at garanti.com.tr
> > > http://www.garantiteknoloji.com.tr
> > > *****************************************************************
> > >
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> ----------------------------------------------------------------------------
> Marc Duchesneau
> Technicien Réseau
> Les Systèmes Électroniques Matrox
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