[mrtg] Re: how can I schedule <5 minute intervals?

Alexander Fichman alexf at ipexsoft.co.il
Wed Oct 27 18:27:15 MEST 1999

Thanx for the verbose and quick response; I am new to this so I have some
more questions:
Are the counters you speak of are device SNMP counters or MRTG counters?
You specify the OID of (what I understand) are the 64bit device counters
(hardcoded in the device' firmware). So, the overflow you talk about is at
what level? MRTG or SNMP-device?


-----Original Message-----
From: Alex van den Bogaerdt [mailto:alex at slot.hollandcasino.nl]
Sent: Wednesday, October 27, 1999 4:34 PM
To: alexf at ipexsoft.co.il
Cc: mrtg at list.ee.ethz.ch
Subject: Re: [mrtg] how can I schedule <5 minute intervals?

Alexander Fichman wrote:
> You mean leave the MRTG config file setting on 5 minutes and just run MRTG
> in less than 5 minute intervals?


You won't get better granularity of the data but you are able to collect
more data.

When possible, use 64-bit counters.  AFAIK this is not yet wide spread.
They are:
ifHCInOctets  (
ifHCOutOctets (

If you have to use 32-bit counters, you may run into problems. One of them
is the maximum rate that you can monitor.  The maximum rate for a 32-bit
counter can be calculated. The maximum value is 2^32-1 == 4294967295.

Sampled every x minutes        maximum rate
(x*60 seconds)             in bps        in bps
1    (60)                 71,582,788   572,662,304
2   (120)                 35,791,394   286,331,152
3   (180)                 23,860,929   190,887,432
4   (240)                 17,895,697   143,165,576
5   (300)                 14,316,557   114,532,456

Other problems will occur, for instance the counter-wrap problem where
MRTG uses the previous value and not the recently collected counter value.
Also, when calling MRTG more often, chances are that you run into
performance problems.  This is why I recommend to use RRDtool.

 / alex at slot.hollandcasino.nl                  alex at ergens.op.het.net \
| work                                                         private |
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