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I'm trying to set up a monitoring system and have been asked to add all of our uplinks in it. most of our switches consists of stacks of about 7 switches. These stacks aren't returning any data.

I run MRTG on the single switches and get back nice graphs same goes for our SAN switches. but the big stacks return nothing but empty logs and empty graphs. It does seem to see which ports are in use because it doesn't return it for unused ports.

Anybody got any idea what is going wrong? it is running on an ubuntu server with the latest MRTG package.

Radim Köhler
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user2477981
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  • You should let us know the MRTG version you are using, also some more data about how you are querying (SNMPv1 or v2?). Also, any error messages being output by MRTG when it runs on these devices, and if you can run snmpwalk on the device from the command line (proviing network connectivity etc) – Steve Shipway Jul 28 '13 at 23:20

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There are several reasons why you might not be getting any data in the MRTG graphs. In order to find out more, you should run MRTG interactively from the command line, and look at the messages produced - is it telling you any error messages? Can you use snmpwalk to successfully query the stack from the commandline?

Possible reasons -

  1. You have the incorrect SNMP community string to access the devices
  2. You have no network access to these devices (routing, firewall, ACL on devices)
  3. You have the wrong SNMP version (use SNMPv2 where possible)
  4. The ports are GigE and your device will only report in SNMPv2 -- and you're using SNMPv1
  5. The stacks are so large that the SNMP times out before returning information. Increase the timeout.
  6. You have added cards or items to the stacks, and this has reenumerated the ports but you have not regenerated the MRTG cfg file, so MRTG is querying nonexistent items. Re-run cfgmaker.
  7. The MaxBytes setting in the cfg file is too low, and the returned data are being ignored. This can happen with some devices that return invalid port details for GigE ports and cause cfgmaker to generate incorrect configurations.

You can set the SNMP version and timeout options in the Target[] definition; see the documentation in http://oss.oetiker.ch/mrtg/doc/mrtg-reference.en.html

Steve Shipway
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