[mrtg] Re: mrtg vs. Linux

[Neil Calvert]

I think I can speak for all list members using Linux and who weren't
previously aware of this by saying

(sounds of sobs of tearful gratitude)

THANK YOU! 

:)

Neil

Eric Seppanen wrote:
> 
> Hi, just wanted to drop a line and get this into the list archives.  It
> details some of the things I learned trying to get mrtg monitoring an i386
> machine running Red Hat Linux 6.0.
> 
> The machine is mostly stock plus all current Red Hat updates, which sadly
> only brings me to kernel 2.2.5.  I installed the ucd-snmp package, version
> 3.6.1, which is part of the Red Hat distribution.  I let mrtg run for a
> week before noticing that the results graphed, while _appearing_ to be
> valid traffic (lots during the day and not much at night), the numbers
> were roughly 1/4 to 1/3 of what they should have been.  However, at times
> the traffic graphed seemed to be somewhat random.  Strange.
> 
> I upgraded to ucd-snmp 3.6.2 with no effect.  I found a patch on the
> ucd-snmp homepage (http://ucd-snmp.ucdavis.edu) that was supposed to fix
> the bug.  Apparently Linux 2.0 doesn't actually keep track of bytes
> transmitted or received, so ucd-snmp reads the number of packets
> transmitted and multiplies it by some constant to get a crude estimate of
> bytes transmitted.  This probably worked fine until Linux 2.2 changed the
> layout of /proc/net/dev and totally broke ucd-snmp.  Getting back on
> track, the patch I found at ucdavis to fix this somehow managed to
> make it worse- not only were the results still wrong, but the transmit
> statistics now went to zero and stayed there.
> 
> I downloaded ucd-snmp 4.0.1 and things worked correctly from there.
> Finally!
> 
> So, things to remember:
> * ucd-snmp 3.6.x are all broken on linux 2.2, even with the patch.
> * if you want perfect statistics don't bother with linux 2.0
> 
> Wishing you better luck than I had,
> Eric Seppanen
> eds at reric.net
> 
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