[mrtg] Re: Mrtg does not display high values of traffic correctly ??
rcc at speedy.net.pe
Fri May 31 03:56:14 MEST 2002
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
----- 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
> > 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
> > the values displayed (also the graph) for the incoming traffic fall down
> > very small values (a few kbps) but, in the orther hand, this does not
> > with the outgoing traffic, that remains displayed in its correct values
> > it's usually not higher than 50Mbps ). This condition returns to
> > 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,
> > logs did not give me any error messages.
> > Do I need a special option in the mrtg config file to handle high values
> > traffic correectly ?
> > Thanks in advance for any help,
> > Richard Cotrina
> > --
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> -------------- -- ---- ---- --- - - - - - -- - - - - - -
> Tony Bourke tony at vegan.net
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