[mrtg] Re: Counter Rollovers

[Jim McAtee]

Thanks.  From the sounds of it, what I'm seeing then must be loss of SNMP
packets.

Does mrtg have any mechanism to deal with missing SNMP responses - such as
requerying the device?  Like I say, I only notice it when the network is
relatively busy.  The traffice is Internet traffic, though, measurable only
in the range of 200-250 kB/s on any given port (HP 2400M switch).  I can't
imagine that it's either the switch or network congestion as the cause of
the packet loss. It seems more likely that the loss is ocurring at the
machine running mrtg, which does get very busy at times (also running mySQL
and email).  Any solutions, short of moving mrtg to a different box?

Jim


----- Original Message -----
From: "Makai József" <jozsef.makai at siemens.com>
To: <mrtg at list.ee.ethz.ch>
Sent: Tuesday, January 14, 2003 2:11 AM
Subject: [mrtg] Re: Counter Rollovers



Hi Jim,

1. mrtg handles the counter rollovers. If the new value of the counter is
less then the previous one, mrtg knows that there was a counter rollover and
according to this counts the result.
But you have to take it into consideration that mrtg can calculate only with
ONE rollover. If the port speed is too high, or the checking period is too
long you can get false results. If the device supports, use the 64 bit
counters.

2. Dropouts can occur when you do not get back the result of an SNMP query.
If the traffic is too high you can loose the snmp packets.

Hope this helps you a bit.

Jozsef

> How does mrtg handle counter rollovers - or does it?
>
> I notice that on a number of very busy interfaces (switch
> ports) that I
> periodically get "dropouts", where the graph will go to zero.
>  I'm wondering if
> these are evidence of the counters rolling over and starting
> again from zero.
>
> Jim
>

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