[mrtg] MRTG bandwidth error

Sean Cheesman scheesman at caeveo.com
Tue Dec 2 04:01:15 CET 2008

If you don't have a lot of interfaces to change, just manually change your config file.  It'll take you all of 5 minutes, and you won't have to rerun cfgmaker.

From: Matthew Petach [mpetach at yahoo.com]
Sent: Monday, December 01, 2008 9:33 PM
To: nv_2030 at yahoo.com; mrtg at lists.oetiker.ch; Sean Cheesman
Subject: Re: [mrtg] MRTG bandwidth error

If your link is a 64kb link, and you change the "bandwidth" statement in your router config,
the next time you run cfgmaker against the device, it will generate correct MRTG configs
with the right MaxBytes statement so that your percentages will be correct.  But you *do*
have to re-run cfgmaker for it to pick up the change, it won't magically know that you've
changed the bandwidth statement on the router.


From: nangineni praneeth <nv_2030 at yahoo.com>
To: "mrtg at lists.oetiker.ch" <mrtg at lists.oetiker.ch>; Sean Cheesman <scheesman at caeveo.com>; Matthew Petach <mpetach at yahoo.com>
Sent: Saturday, November 29, 2008 10:01:13 AM
Subject: Re: [mrtg] MRTG bandwidth error

Thank you..Yes i am using a cisco router......so it means probably that in the ifspeed OID on this cisco 2811 router the speed was 193kbps.......so how do i get the percentage then

I have seen in other posts that diving the OID helps for eg:

OID / 64kbps(After i change the bandwidth)...will the graph change too if  give this in the config file...or should i use the option[xx].dorelpercent


--- On Fri, 11/28/08, Matthew Petach <mpetach at yahoo.com> wrote:
From: Matthew Petach <mpetach at yahoo.com>
Subject: Re: [mrtg] MRTG bandwidth error
To: nv_2030 at yahoo.com, "mrtg at lists.oetiker.ch" <mrtg at lists.oetiker.ch>, "Sean Cheesman" <scheesman at caeveo.com>
Date: Friday, November 28, 2008, 11:14 PM

MRTG doesn't look at the clock rate, it looks at the ifSpeed SNMP OID;
to change that, on a Cisco, use the "bandwidth" statement in the interface
configuration section.  If it's not a Cisco, you'll need to consult your
vendor documentation to figure out how to change the value reported
by the ifSpeed OID.


From: nangineni praneeth <nv_2030 at yahoo.com>
To: "mrtg at lists.oetiker.ch" <mrtg at lists.oetiker.ch>; Sean Cheesman <scheesman at caeveo.com>
Sent: Friday, November 28, 2008 7:58:33 AM
Subject: Re: [mrtg] MRTG bandwidth error

Thank you very much...But why is it taking a T1 link bandwidth when i specified the clockrate to be 64kbps??......I know that i can edit the cfg file later and set the MAX bytes to   to 64kbps but i thought MRTG would calculate the interface B.W automatically when i polled the router...

--- On Fri, 11/28/08, Sean Cheesman <scheesman at caeveo.com> wrote:
From: Sean Cheesman <scheesman at caeveo.com>
Subject: RE: [mrtg] MRTG bandwidth error
To: "nv_2030 at yahoo.com" <nv_2030 at yahoo.com>, "mrtg at lists.oetiker.ch" <mrtg at lists.oetiker.ch>
Date: Friday, November 28, 2008, 9:21 PM

193kbytes = 1536kbps (x8)
70.2kbps / 1536kbps = .0045
.0045 = 4.5%
From: mrtg-bounces at lists.oetiker.ch [mrtg-bounces at lists.oetiker.ch] On Behalf Of nangineni praneeth [nv_2030 at yahoo.com]
Sent: Friday, November 28, 2008 10:28 AM
To: mrtg at lists.oetiker.ch
Subject: [mrtg] MRTG bandwidth error

Hello everyone i have found MRTG reporting a small error on my bandwidth.......I configured a small campus enterprise network with collapsed core design(in a lab environment).........I used a frame relay connection to connect to my branch office..I have specified the clock rate to be 64kbps.....But when i was collecting the interface traffic from my enterprise edge MRTG was reporting the max traffic below the graph to be 70.2 kbps....How is it possible?Because the serial link was supposed to be at 64kbps(the clock rate which i gave)......This was the outbound traffic  MRTG reported.........

Out     70.2 kb/s (4.5%)        37.8 kb/s (2.4%)        63.0 kb/s (4.1%)

The max speed MRTG gave of the interface was 193.0kbytes.Also kindly please explain what the percentage represents...I have been pulling my hair and doing all sorts of calculation to find out what the percentages exactly means and what is it exactly representing


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