[mrtg] Re: bandwidth question

Greg.Volk at edwardjones.com Greg.Volk at edwardjones.com
Wed May 14 22:31:38 MEST 2003

}I then tested some backups. I watched for over 10 minutes, 
}with overlap on the MRTG 5 minute interval, and the lowest 
}rate I ever saw come through to that interface was 125 Mbits 
}per second, and the highest was 267 Mbits per second.  Great 
}it works!  I verifed these results by using the SolarWinds 
}Bandwidth monitor tool, as well as with GlancePlus 
}(measurement software for HP-UX), so I feel pretty good about 
}two different tools seeing the same results.
}Yet when I checked the MRTG graph, it only showed 111 
}Mbits/sec during the ftp test, and 104 Mbits/sec during the 
}backup test.
}Any ideas as to why it isn't displaying what I think it 
}should, specifically higher values?  It is a 5 minute average 
}right?  Both times I made sure the tests lasted at least 10 
}minutes to cover at least one 5 minute window of high bandwidth.
I couldn't ascertain whether or not you're polling this interface
with 64 bit counters. If you aren't, then the maximum you'll see
on MRTG is ~114 megabits/sec. A 32 bit counter running faster than
that will roll in less than five minutes and give bogus results.

Try this when building your config:

cfgmaker --snmp-options=:::::2 public at device

That should generate a config with 64 bit counter polling. Of
course, your switch/router will need to support the big counters,
but chances are it does if it has gig-e interfaces.

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