[mrtg] Re: Counter Rollovers

[Brander, Eric]

MRTG can handle single roll-overs just fine... its when the counter rolls 2
or more times within a polling interval that there is a problem.  I don't
remember the specific numbers, but if you get over 180 Mbps or maybe it was
over 200 Mbps, your counters will reset twice within 300 seconds using a
32-bit counter. (I'm to lazy and tired to do the math to find Try to use
64-bit counters if they are available on high speed links, or use RRDTool
and poll more frequently on devices that don't have 64-bit counters.  I'm
currently doing a 1-minute interval on some gigabit links and haven't had
counter wrap problem since, even doing a sustained 350 Mbps.  However, I
haven't measured the added load of that frequent polling.  YMMV.

If you have 64-bit counters, check using SNMP2 in the MRTG Reference
documentation. (:::::2)

Eric Brander
ACS
Texas CHIP Account
Sr. Communications Engineer - Information Systems Department
512.336.3331
Eric dot Brander at acs-inc dot com


-----Original Message-----
From: Jim McAtee [mailto:jmcatee at mediaodyssey.com]
Sent: Monday, January 13, 2003 2:42 PM
To: mrtg at list.ee.ethz.ch
Subject: [mrtg] Counter Rollovers



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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