[mrtg] gigabit links not graphing properly

Steve Shipway s.shipway at auckland.ac.nz
Tue Aug 19 00:27:52 CEST 2008

Almost certainly counter rollover.  Make sure you are using SNMPv2 (add :::::2 to the end of the Target definition) to use the HC counters, else you'll get it dropped in chunks of ~140Mb, which would tally with what you're seeing.

In the time of a 5-min poll, 32-bit counters will roll over if network throughput is over about 140Mbps.  Therefore you need to use 64bit counters if your link is >100Mbps.  64 bit counters are only available using SNMPv2 or higher.


From: mrtg-bounces at lists.oetiker.ch [mailto:mrtg-bounces at lists.oetiker.ch] On Behalf Of Doug Lessans
Sent: Tuesday, 19 August 2008 07:23
To: mrtg at lists.oetiker.ch
Subject: [mrtg] gigabit links not graphing properly

Gigabit link on  Cisco 6506 switch does not indicate correct bandwidth utilization.    I "show interface" for the interface and see ~400 mb/s, but the graph indicates ~90mb/s.   Any help would be appreciated.    Thank you.   Doug
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