# [mrtg] SV: Re: mathematical expressions for Collision statistics

Foverskov, Esben, esf esf at esbkomm.dk
Tue Nov 6 17:25:39 MET 2001

```Hi,

I think that will work. If your equipment supports those stats, that is.
Give it a try!

-----Oprindelig meddelelse-----
Fra: Tom McGovern [mailto:tom at mcgov.net]
Sendt: 6. november 2001 17:23
Til: Foverskov, Esben, esf
Emne: RE: [mrtg] Re: mathematical expressions for Collision statistics

Hi,

Aha ! I see, you are exactly right. I myself was starting to wonder about

In the rmon group of MIB2:

etherStatsPkts (counter)
This read-only MIB object displays the total number of packets (including

etherStatsCollisions (counter)
This read-only MIB object displays the best estimate of the total number of
collisions on this Ethernet segment.

Therefore, the formula could be:

100 * etherStatsCollisions / etherStatsPkts

Tom

-----Original Message-----
From: mrtg-bounce at list.ee.ethz.ch [mailto:mrtg-bounce at list.ee.ethz.ch]On
Behalf Of Foverskov, Esben, esf
Sent: Tuesday, November 06, 2001 10:54 AM
To: 'Tom McGovern'; mrtg at list.ee.ethz.ch
Subject: [mrtg] Re: mathematical expressions for Collision statistics

Hi,

Don't quite know whether the formula would work, but is this really what you
want? the etherStatsCollisions counts the number of collisions that have
occurred, right? And you are dividing this by the total number of bytes in
and out the interface. That doesn't make sense. So looking at the units
only, you're dividing packets with bytes, giving you the unit packets/byte.
You need to divide packets with packets to get a percentage (no units). How
you would go about doing that is another question entirely ;O)

-----Oprindelig meddelelse-----
Fra: Tom McGovern [mailto:tom at mcgov.net]
Sendt: 6. november 2001 16:24
Til: mrtg at list.ee.ethz.ch
Emne: [mrtg] mathematical expressions for Collision statistics

Hi,

I'm trying to measure the amount of ethernet collisions as a percentage of
the overall interface traffic. I think this is what I want:

Target[13-col.192.168.254.127]:etherStatsCollisions.113:public at 192.168.254.1
27 / ifOutOctets.113:public at 192.168.254.127 +
ifInOctets.113:public at 192.168.254.127 &
etherStatsCollisions.113:public at 192.168.254.127 /
ifOutOctets.113:public at 192.168.254.127 +
ifInOctets.113:public at 192.168.254.127

Note I am just graphing the same variable twice fo simplicity.

But, how will MRTG interpret this formula ? Can I use parentheses in my
formular ?

Basically I need the following:

etherStatsCollisions / (ifInOctets + ifOutOctets) * 100

Thanks,

Tom McGovern

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