[mrtg] Re: Unexpected drop-outs in graphs

Tue Jun 17 12:20:24 MEST 2003

Your analysis certainly confirms my original thoughts.

I ran STG  (SNMP Traffic Grapher) version 1.4.5 to monitor the router overnight and its interesting that it does not show any drop-outs.

Does anyone know how STG handles the counter wrap?

Regards,

Nick Earle

                    Alex van den                                                                                   
                    Bogaerdt             To:     mrtg at list.ee.ethz.ch                                              
                    <alex at ergens.o       cc:     (bcc: Nick Earle/London/GB/BAT)                                   
                    p.het.net>           Subject:     [mrtg] Re: Unexpected drop-outs in graphs                    

                    16/06/2003                                                                                     
                    17:30                                                                                          

On Mon, Jun 16, 2003 at 05:06:12PM +0100, Nick Earle wrote:
>
> I'm having a problem with MRTG which is resulting in drop-outs in my graphs. The drop-out appear to occur after a specific amount of traffic has passed, as the area between each drop-out appears to be the same. Please take a look at the attached graph to see what I mean.

To me it appears this happens after 2^32 octets.

Look attime 12 to 20:
12 to 20: roughly 8 hours at 1200 Kbps:  8*3600*1200*1000/8 = 4320000000
20 to 01: roughly 5 hours at 1800 Kbps:  5*3600*1800*1000/8 = 4050000000
11 to 15:30 : roughly 4.5 hours at 2000 Kbps: 4.5*3500*2000*1000/8 = 3937500000

All these numbers are close to 2^32 which is 4294967296.

This doesn't help much but at least the "specific amount of traffic" can
now be guessed to be 2^32 octets.

Could it be that you are using 64-bit counters that wrap at 2^32 ?

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