[mrtg] Strange MRTG problem

Steve Shipway s.shipway at auckland.ac.nz
Wed May 15 05:34:55 CEST 2013

A few thoughts


1.       You’ve just told the world your SNMP community string.  Oops.

2.       It certainly looks a bit like an SNMPv1 issue, though that would generally top off about 120Mbps.  However the config seems to use v2 correctly.

3.       Are you absolutely certain that both graphs relate to the same port?  Possibly there is some confusion in the settings?

4.       Look at the two graphs close up.  Are they exactly the same for low values, then lose it for high values?  If so, maybe its using SNMPv1 anyway.  If not, maybe you’re graphing something different.

5.       Which version of MRTG do you have?  Possibly an old one is not handling things correctly.  Get a copy of 2.17.x installed and see if the problem goes away.

6.       There’s always the possibility that Cacti is getting it wrong, so check there as well.

7.       Is it a bits/bytes issue?  If Cacti is showing 8x the MRTG value, maybe MRTG is showing in bytes. Though you have ‘options bits’.

8.       What frontend are you using for MRTG/RRD?  Some, notably Routers2.cgi in earlier versions, want the Target line to come first in the stanza.  Try rearranging them this way, maybe the Options line is getting ignored and you’re viewing in bytes/sec.







Steve Shipway

ITS Unix Services Design Lead

University of Auckland, New Zealand

Floor 1, 58 Symonds Street, Auckland

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Email:  <mailto:s.shipway at auckland.ac.nz> s.shipway at auckland.ac.nz

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From: mrtg-bounces+s.shipway=auckland.ac.nz at lists.oetiker.ch [mailto:mrtg-bounces+s.shipway=auckland.ac.nz at lists.oetiker.ch] On Behalf Of Simon Westlake
Sent: Wednesday, 15 May 2013 2:26 p.m.
To: mrtg at lists.oetiker.ch
Subject: [mrtg] Strange MRTG problem




It's been a long time since I used MRTG (I've been writing directly to rrds for a long time now) but an old employer of mine asked me to troubleshoot a legacy MRTG setup and I'm having a strange problem with it I cannot decipher.


I am graphing a port in two ways. One is in Cacti, one is with MRTG. Both are using 64bit counters (I have even setup the MRTG configuration to specifically use the HC OIDs rather than assuming they are being queried by specifying :::::2)


In Cacti, I get the correct value (approximately 700-800Mbps per second.) In MRTG, it is never more than 190-200Mbps.


My MRTG configuration looks like this:



Forks: 30

Refresh: 300

Interval: 5

MaxAge: 999999999999999999999999

SnmpOptions: retries => 1, timeout => 1

LogFormat: rrdtool



Options[DAS-c3229-bandwidth]: growright,bits,nolegend,nobanner,nopercent

Directory[DAS-c3229-bandwidth]: DAS-c3229

Target[DAS-c3229-bandwidth]: at

Extension[DAS-c3229-bandwidth]: php

Suppress[DAS-c3229-bandwidth]: y

Title[DAS-c3229-bandwidth]: Bandwidth Utilization

Maxbytes[DAS-c3229-bandwidth]: 200000000000000000

AbsMax[DAS-c3229-bandwidth]: 200000000000000000


I have tried tweaking a lot of things and I can't seem to figure out what's going on. Any insight would be appreciated as I'm 2+ days into troubleshooting this thing and it's driving me crazy. Thanks!

- Simon Westlake

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