[mrtg] Re: Mrtg does not display high values of traffic correctly ??

[Richard Cotrina]

Hi :

Thanks for all your answers. Now, using SNMP v2c, my graph is displaying the
values normally, without any breaks.

Is it valid for a Target[ ] that is a result of an arithemtical operation
too ?, I mean :

Target [abc]: oid1&oid2 at router_a + oid1&oid2 at router_b + oid1&oid2 at router_c

Should it be ? :

Target [abc]: oid1&oid2 at router_a:::::2 + oid1&oid2 at router_b:::::2 +
oid1&oid2 at router_c:::::2

Because I am having the same problem in a Target like that, and using SNMP
v2c seems not to solve the problem.

Thanks again for your help

Richard Cotrina

----- Original Message -----
From: "tony bourke" <tony at vegan.net>
To: "Richard Cotrina" <rcc at speedy.net.pe>
Cc: <mrtg at list.ee.ethz.ch>
Sent: Thursday, May 30, 2002 1:26 PM
Subject: [mrtg] Re: Mrtg does not display high values of traffic correctly
??


>
> Hi Richard,
>
> The answer, as people have already stated, is to use SNMPv2.
>
> Here is a blurb on the technical reasons for the errors with v1:
>
> One limitation to keep in mind is that with SNMPv1 MRTG or any other SNMP
> program) cannot accurately measure bandwidth above about 114 Mbps
> (Megabits per second) based on 5-minute intervals. 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.  Using SNMPv2's 64-bit counters will overcome this.
>
>
>
> On Thu, 30 May 2002, Richard Cotrina wrote:
>
> >
> > Hello :
> >
> > I am using mrtg to monitor the traffic going and coming through a STM-1
POS
> > interfaz in my Cisco Router. It was working fine until the values of
> > incoming traffic started to be above 100Mbps.
> >
> > The matter is that suddenly and without giving any errors in the log
file,
> > the values displayed (also the graph) for the incoming traffic fall down
to
> > very small values (a few kbps) but, in the orther hand, this does not
happen
> > with the outgoing traffic, that remains displayed in its correct values
(
> > it's usually not higher than 50Mbps ). This condition returns to
normality
> > without any reason, and also when the traffic is lower than 100Mbps.
> >
> > The result of this, is that my mrtg graphs shows an apparently loss of
> > traffic, but it is not caused by any traffic interruption, because the
> > outgoing traffic is displayed continously.
> >
> > I was using mrtg 2.9.17 when it started to happen, then I upgraded to
> > 2.9.18pre11 and got the same results.
> >
> > Does anyone have an idea on what is going on ?  As i mentioned before,
the
> > logs did not give me any error messages.
> > Do I need a special option in the mrtg config file to handle high values
of
> > traffic correectly ?
> >
> > Thanks in advance for any help,
> >
> > Richard Cotrina
> >
> > --
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> -------------- -- ---- ---- --- - - - -  -  -- -  -  -  -   -     -
> Tony Bourke tony at vegan.net
>
>
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