[mrtg] Re: Router appears to drop out, but provider sayes its ok

Nick Earle Nick_Earle at bat.com
Fri Apr 25 16:47:15 MEST 2003

This link currently has a CIR = 3Mb and the Circuit is 4Mb so I've set the MaxBytes and AbsMax values as follows:-

     MaxBytes  384000
     AbsMax    512000

Which I thought would allow enough scope for bursting.


Nick Earle

                    Daniel J McDonald                                                                                     
                    <dan.mcdonald at austine       To:     Nick Earle <Nick_Earle at bat.com>                                   
                    nergy.com>                  cc:     (bcc: Nick Earle/London/GB/BAT)                                   
                                                Subject:     Re: [mrtg] Router appears to drop out, but provider sayes    
                    25/04/2003 13:22             its ok                                                                   

On Fri, 2003-04-25 at 05:18, Nick Earle wrote:
> I'm using MRTG to monitor around 150 routers.
> On a couple of the bigger routers (CIR=4Mb) I'm getting 'dropouts' every 4 hours. The period between dropouts is proportional to the amount of traffic, so if there is more traffic the dropouts appear more frequently. Our network service provider is assuring me that there dropouts are not real!

Do you have maxbytes = CIR, or are you setting maxbytes = PIR?

If Maxbytes=CIR and you burst above CIR, MRTG will assume the
information it received was bogus and will discard it.

If you want to maintain the look of your graphs, you  might try setting
maxbytes=CIR and Absmax=PIR.

> I was wondering if this might be caused by counter overflow?
not at 4mb/s.  134mb/s, sure, but not 4.

> Does anyone now if there is a setting I can use to handle counter overflows more elegantly?
> Regards,
> Nick Earle
Daniel J McDonald, CCIE 2495, CNX
Austin Energy

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