Syed Jahanzaib Personal Blog to Share Knowledge !

June 20, 2016

MRTG graph 120M Limitation

Filed under: Linux Related — Tags: , — Syed Jahanzaib / Pinochio~:) @ 11:00 AM


If you are using MRTG and have gigabit network, you may notice that mrtg graphs will not show you traffic above then 120mb.  This is a common problem caused by 16-bit counter rollover. By default MRTG polls the device every 5min using SNMPv1, then a traffic greater than 120 Mbps will cause the 16 bit counter to wraparound in this time window.

therefore , MRTG only displays the lower traffic as it cannot tell how many times the counter has rolled over.

There are two workarounds to over come this issue.

  1. SNMP V2
  2. RRD

Quick Workaround:

I used SNMPv2. This is the best option, if your device supports it (Mikrotik do support SNMP v2). If using SNMPv2, then you can use the 64bit counters, which will not wrap around.

To do this, add


(5 semicolons and 2) as a suffix to your Target definition to specify SNMPv2.

Working Example:

To edit existing configuration file.

Target[]: #eth0:public@

or with cfgmaker

cfgmaker public@

I will write on RRD later which is the best option in my opinion , specially for heavy networks.

Syed Jahanzaib

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