[mrtg] Re: Monitoring 5G bps network

[tony bourke]

Hi All,

I've posted this before, but I think Sungchul might find this useful as
well.  Here is why MRTG/SNMP can't go past about 115 Mbps with 32-bit
counters:
-------------------------------------------------------------------
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. (2^32 = 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.

Tony

On Wed, 8 Nov 2000, Sungchul Park wrote:

> 
> Hello.
> I'm s/w engineer in Korea and first here.
> My customer has a big network that the traffic is over 2G bits per second.
> In next year, his network will be expanded up to 5G bps.
> He want to monitor his network with MRTG, but he think MRTG can not handle
> such a big traffic data, because MRTG use integer to store values.
> He also want to use gnu/linux i386 for running MRTG.
> Could I solve this problem? I have to meat him tomorrow afternoon.
> 
> ----------------
> Park, Sungchul / mailto:scpark at gen128.com
> gen128, inc. - The internet company powered by open source.
> http://www.gen128.com / Voice : +82-2-3017-0128 / Fax : +82-2-3017-1128
> 238-9 poi kangnam, #601 poongjoen bldg., Seoul 135-250, Republic of Korea
> 
> 
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-------------- -- ---- ---- --- - - - -  -  -- -  -  -  -   -     -
Tony Bourke				tony at vegan.net




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