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

Alex van den Bogaerdt alex at slot.hollandcasino.nl
Wed Oct 27 18:50:01 MEST 1999

> Are the counters you speak of are device SNMP counters or MRTG counters?

I'm not sure if MRTG is 64 bit ready but from some of the responses on the
list I think it is.  I was referring to SNMP counters.  They both have to
be able to use 64-bit values or you loose.

> 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?

SNMP, and perhaps MRTG.

In your config file, you will see something like 'Target[x]: 1:public at router'.
This is short hand for
   Target[x]: at router
You may be able to use those other OIDs.

Scan the list for the various discussions on OIDs, MIB and more.

>> Alex, talking about calling MRTG more often than once per 5 minutes while
>> not reconfiguring MRTG to store at that same interval:

>> 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 |
| My employer is capable of speaking therefore I speak only for myself |

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