[mrtg] MRTG not detecting counter wrap

Bjorn Nordbo bn at nextra.com
Tue Dec 19 19:04:19 MET 2000

I use an external script to extract data from files dumped by a
routers bulkstats feature. From time to time, the router will
choke and return an empty file (only schema, no data) and in
the next file, the counters will have wrapped. Let me illustrate:

% wc-generic myrouter.977230250 6
% wc-generic myrouter.977230799 6
% wc-generic myrouter.977231105 6

First the program will return correct data (all the files here
are used for debugging), then it comes to the empty file, returning
nothing and finally correct data againg, but after a counter reset.

What I don't get is why MRTG doesn't detect this wrap, and the graps
are flawed by enormous spikes. Can anyone please explain to me how
MRTG detects counter wraps, and/or point me towards the code that
does this?

Solaris 2.8/MRTG 2.9.4/rrdtool 1.0.28

Any help appreciated!

Bjørn Nordbø  -  IP Development  -  Nextra Norway

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