[mrtg] 114 Mbps: Strange grpahs

[George Nease]

Lars Holmström recently covered this pretty well, so I'll quote him; it
perfectly describes what we are seeing here (and maybe what you're seeing),
and why we're converting to RRD:

"One limitation to keep in mind is that the default configuration file
generated
by MRTG cannot accurately measure bandwidth above about 114 Mbps (Megabits
per
second). The reason is that the default interface counter is a 32-bit
number,
and a 32-bit number will rollover twice in a period of 5 minutes at more
than
114 Mbps. (232 = 4,294,967,296 bytes, multiplied by 8 (bits in a byte),
divided
by 300 seconds in 5 minutes, is 114,532,641 bits per second, or roughly 114
Mbps.) MRTG or any other SNMP program cannot correctly account for a double
rollover. The graph will appear to peak at about 114 Mbps and never go
beyond
that, when in reality the interface could be running well beyond that rate.
To
get around this, you must change the configuration file to pole a special
64-bit
interface counter, or poll MRTG more frequently than 5 minutes."

(by Lars Holmström [lars.holmstrom at flysta.net])

-----Original Message-----
From: Guðmundur Ö. Ingvarsson
[mailto:gudmundur.ingvarsson at islandssimi.is]
Sent: Thursday, May 24, 2001 9:02 AM
To: mrtg at list.ee.ethz.ch
Subject: [mrtg] Strange grpahs



Does anyone know how to get strange empty lines from the mrtg day graph.

I get strange cuts into the graphs like traffic went down even though it
didn´t

Kveðja / Regards

======================================
Guðmundur Örn Ingvarsson
Chief technician of daily operations /
Rekstrarstjóri á rekstrarborði
Íslandssími hf
Web Site - http://www.islandssimi.is
E-Mail - gudmundur.ingvarsson at islandssimi.is
Buisness phone - +354 595 5074
Mobile phone - +354 820 5074
======================================


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