[mrtg] Re: Starting/Stopping mrtg does funky stuff to archived data??

[Tim Kennedy]

On Sat, 11 Dec 1999, Dan Wentzel wrote:

> Hello all,
> 
> 1 - The data collected since June was still there and there were repeated values (i.e.
> a flat line for the off-period).  The new data was added to the logfile for each 5 minute
> firing of the cron and everything went along fine.  Everything BEFORE the cron was
> disabled is still there - no lost data.
> 
> 2 - The data collected since June was wiped out (everything set to zero in monthly
> and yearly), but there was a flat line (repeated values) during the switch off period...
> New data is added by the cron like normal.  Everything BEFORE the cron was 
> disabled is gone, but everything DURING the cron being disabled is still there (those
> repeated values) - partial (well, more than partial) data lost.
> 
> 3 - Everything is wiped out and the whole thing starts from scratch.  Everything BEFORE,
> and DURING the cron being disabled is gone - total data loss.....
> 
> Is this because of the old version I'm running?  How long must the cron be off to cause
> this?  Before the next firing of the cron?

Probably not a cron error.   From the symptoms you've described, you may
have had your ifIndexes change.  That is, the snmp instance of the
interfaces.

At the time that when the cron job was commented out, did your router
reboot, or have any hardware swapped out?  Perhaps an interface card?
Did the config of the router change in any way?  Did you add any
interfaces?  Remove any?

All of those things can cause your ('interface' => 'snmp instance')
relationship to change.   That is, say that in your config ehternet0 had
instance 1. (Target[ezwf] 1:public at router) and you added another ethernet
card to your router.  Perhaps the one that was 1, now became 2, and it's
lable changed to ethernet1.  You would be creating new logs for the new
interface, thus explaining the two errors, and no historical data, and
you would have errored data for the new interface, that was using the old
interfaces log files.   As for the flat lines, MRTG will use the last
recorded number to fill empty sections of logfile.  Thus if you didn't
poll for a few days, you'd get a flatline at the value of the last poll.

Check your router, rebuild your config.  If you can, copy the old logfiles
to the new interface's logfile.  Or upgrade your MRTG to the latest, where
you can track interfaces by IP address.

-Tim

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