[mrtg] infOutOctets,infInOctets variable confusion

Nik Martin nik at winshack.net
Sun Dec 1 05:22:21 MET 2002

Hello mrtg list,

I have Google Searched the list archives and found nothing that answered my
somewhat simple question, so I figured I'd post here.

Here goes:

According to the RFC describing these variables (RFC 1213), these variables
count bytes in and out of an interface since the device came online (was
booted, etc).  Knowing this, we then measure the value at regular
intervals(5 minutes in the case of MRTG).  Does MRTG then just divide the
delta between two reporting intervals by the number of seconds in the
interval to determine bytes/second average transfer rate for the period?


at 01:00 > mrtg reads 10,000 bytes out
at 01:05 > mrtg reads 15,000 bytes out
at 01:10 > mrtg reads 32,000 bytes out
at 01:15 > mrtg reads 38,000 bytes out

    interval 1 shows   5,000 byte delta,   5,000/(5*60) = 16.66 bytes/sec
average tranfser rate for the period
    interval 2 shows 17,000 byte delta, 17,000/(5*60) = 56.66 bytes/sec
average tranfser rate for the period
    interval 3 shows   6,000 byte delta,   6,000/(5*60) = 20 bytes/sec
average tranfser rate for the period

How does MRTG handle these counters getting reset when the device being
monitored reboots?


I ask these questions because I need to round-robin a set of  network
devices from Windows, querying these parameters and feeding the results to
MRTG.  MRTG won't be querying the devices directly

Thank you,
Nik Martin

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