[mrtg] [FORGED] Re: [FORGED] MRTG and IT Watchdog sensor

Steve Shipway s.shipway at auckland.ac.nz
Tue Nov 24 20:13:04 CET 2015

Your device is not responding to the SNMP queries; this means a configuration error in either the device or in your Target line.

Check your device is contactable by ping; that there is no SNMP ACL in place preventing you; that you have the correct community string; that the IP is correct.

Try using snmpwalk to browse the OID from the commandline to test.


Steve Shipway
University of Auckland ITS
UNIX Systems Design Lead
s.shipway at auckland.ac.nz<mailto:s.shipway at auckland.ac.nz>
Ph: +64 9 373 7599 ext 86487

From: mrtg [mrtg-bounces+s.shipway=auckland.ac.nz at lists.oetiker.ch] on behalf of Roger Smith [rogertcoe at gmail.com]
Sent: Wednesday, 25 November 2015 5:44 a.m.
To: mrtg at lists.oetiker.ch
Subject: [FORGED] Re: [mrtg] [FORGED] MRTG and IT Watchdog sensor

I also tried the OID themselves:

Target[]: at<mailto: at>

I got:
2015-11-24 08:44:18 -- SNMP Error:
receiving response PDU: An existing connection was forcibly closed by the remote host.
SNMPv1_Session (remote host: "" [].161)
                  community: "tcoe-snmp"
                 request ID: 1669607121
                PDU bufsize: 8000 bytes
                    timeout: 2s
                    retries: 5
                    backoff: 1)
 at c:/mrtg/bin\..\lib\mrtg2/SNMP_util.pm line 497
2015-11-24 08:44:18 -- SNMPGET Problem for sysUptime sysName on tcoe-snmp at
 at c:\mrtg\bin\mrtg line 2330
2015-11-24 08:44:18 -- 2015-11-24 08:44:18: ERROR: Target[][_IN_] ' $target->[0]{$mode} ' did not eval into defined data
2015-11-24 08:44:18 -- 2015-11-24 08:44:18: ERROR: Target[][_OUT_] ' $target->[0]{$mode} ' did not eval into defined data

Date: Fri, 20 Nov 2015 21:36:46 +0000
From: Steve Shipway <s.shipway at auckland.ac.nz<mailto:s.shipway at auckland.ac.nz>>
To: Roger Smith <rogertcoe at gmail.com<mailto:rogertcoe at gmail.com>>, "mrtg at lists.oetiker.ch<mailto:mrtg at lists.oetiker.ch>"
        <mrtg at lists.oetiker.ch<mailto:mrtg at lists.oetiker.ch>>
Subject: Re: [mrtg] [FORGED]  MRTG and IT Watchdog sensor
        <5820DC553954E44FA1A36C78323AD148A3F955F5 at uxcn10-6.UoA.auckland.ac.nz<mailto:5820DC553954E44FA1A36C78323AD148A3F955F5 at uxcn10-6.UoA.auckland.ac.nz>>
Content-Type: text/plain; charset="iso-8859-1"

Target[]: tempSensorTemp:tcoe-snmp at<mailto:tempSensorTemp%3Atcoe-snmp at><mailto:tempSensorTemp%3Atcoe-snmp at<mailto:tempSensorTemp%253Atcoe-snmp at>>

You must always give exactly two metrics to MRTG per Target (this is historical, because originally this was inbound and outbound data for network traffic).  If it is a single value, either duplicate it, or use pseudoZero.

Target[]: tempSensorTemp&pseudoZero:tcoe-snmp at<mailto:tempSensorTemp%26pseudoZero%3Atcoe-snmp at><mailto:tempSensorTemp%3Atcoe-snmp at<mailto:tempSensorTemp%253Atcoe-snmp at>>

This is also assuming, of course, that the symbolic name tempSensorTemp can be expanded to an OID; for this to work, you need to have the MIB properly installed or referred to in the MRTG config file.  Otherwise, you can always use the numerical OID instead.

Now, your OID actually returns the value in deci-degrees, so you need to divide by 10 before storing to make the value an SI unit (Best Practice is to store values as SI units).

Target[]: tempSensorTemp&pseudoZero:tcoe-snmp at<mailto:tempSensorTemp%26pseudoZero%3Atcoe-snmp at>  /  10
<mailto:tempSensorTemp%3Atcoe-snmp at<mailto:tempSensorTemp%253Atcoe-snmp at>>

The spaces around the '/' are required.  This will mean the value is stored in degrees, and will display the correct numbers.  However, if you are not using RRDTool and are just using native MRTG, decimals are not supported in the backend storage, and so you might instead need to do

Factor[]: 0.1

... which will divide by 10 at graphing time instead.

Since you do not want to graph the second item, just use the 'noo' ('No outgoing') option to suppress it.

Options[]: gauge growright noo



Steve Shipway
University of Auckland ITS
UNIX Systems Design Lead
s.shipway at auckland.ac.nz<mailto:s.shipway at auckland.ac.nz><mailto:s.shipway at auckland.ac.nz<mailto:s.shipway at auckland.ac.nz>>
Ph: +64 9 373 7599 ext 86487<tel:%2B64%209%20373%207599%20ext%2086487>

Roger Smith
Director, Information Systems
Tulare County Office of Education
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