[mrtg] MRTG Graph and Bandwidth > 120 Mbps

Steve Shipway s.shipway at auckland.ac.nz
Thu Oct 14 06:10:33 CEST 2010

> First, let me apologize if the topic has been covered and resolved
> before that I don't know of.

This one should be at the top of the FAQ... if we had a FAQ, that is.  Prepare for several dozen replies giving you the answer...

> I've  been experiencing that: if the bandwidth goes larger than 120
> Mbps, MRTG would not display it correctly while another software I
> tried such as "Interface Traffic Indicator" would.

When using a normal 16bit network counter, it will roll over within the 5min polling window if network throughput is over approx 130Mbps.  This causes the problems you are noticing.

Solution: Use SNMPv2 which has the 64bit HC counters.  Cfgmaker will handle these automatically if you tell it to use SNMPv2.

1) add :::::2 to the end of your Target definition to specify using SNMPv2, or
2) pass --snmp-options=':::::2' to cfgmaker to tell it to generate SNMPv2 configuration files, or
3) Change polling interval to 1 minute (Interval: 1).  This will require you to delete your old .rrd files and change your polling frequency though so is probably more trouble than its worth.

This will solve your problem.


Steve Shipway
ITS Unix Services Design Lead
University of Auckland, New Zealand
Floor 1, 58 Symonds Street, Auckland
Phone: +64 (0)9 3737599 ext 86487
DDI: +64 (0)9 924 6487
Mobile: +64 (0)21 753 189
Email: s.shipway at auckland.ac.nz
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