[mrtg] Strange MRTG problem

[Alex van den Bogaerdt]

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

In addition to what Steve already said:

Monitor your RRD file. Look for the counter values being put in, and the 
timestamps this happened (rrdtool lastupdate, or rrdtool info)

Do the timestamps have expected values?  If not, your crontab may need to be 
altered.

Then look at the counter values being collected. Do the computations 
yourself (subtract previous counter value from the current counter value, 
subtract previous timestamp from the current timestamp, compute 
delta(countervalue)/delta(timestamp).  Is the result close to what you 
expect to get, or is it close to what MRTG reports?  This should help you 
figure out if it is collecting the counters which fails or if it is 
processing them further which fails.

Also check your config file for typos. Use any tool you feel comfortable 
with, except your own eyes and brains; let the machine do the work (e.g. 
grep). Maybe you find a typo which results in different behaviour than you 
expect. That typo could be in another part of your config, overriding what 
you think you have set for DAS-c3229.