[mrtg] Can not determine ifNumber and duplicate entries of IP-Ifindex at the .ok files

Steve Shipway s.shipway at auckland.ac.nz
Mon Jan 31 22:13:49 CET 2011

> 2011-01-31 13:24:01: WARNING: Can not determine ifNumber for
> public at router:::2::1   ref: 'Ip'       key: ''

This message means that it cannot work out how to (uniquely) determine which interface to monitor when it's been given the IP address as a key.

This can be caused by 2 things --

1. There really ARE two interfaces with the same key.  In your case, this is not true, though it can happen in some cases, eg when a description or MAC address is used as a key.
In this case, the solution is to use a different key to uniquely identify the interface.

2. The .ok cache file contains invalid data, that cannot be removed.  This is your problem.  This can be caused when the device is reconfigured, or new interfaces added etc, causing a reenumeration of the interfaces.  Possibly, the file is somehow undeleteable or not updateable (check permissions)?
In this case, the solution is to DELETE THE .OK FILE, which will cause it to be re-created automatically with the correct data.  This should happen normally, but can sometimes get confused -- check you have the latest version of MRTG (or at least 2.16.2 )


Steve Shipway
ITS Unix Services Design Lead
University of Auckland, New Zealand
Floor 1, 58 Symonds Street, Auckland
Phone: +64 (0)9 3737599 ext 86487
DDI: +64 (0)9 924 6487
Mobile: +64 (0)21 753 189
Email: s.shipway at auckland.ac.nz
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