[mrtg] Follow up diagnosis of traffic volume

[mrtglist at encambio.com]

Hello list,

After setting up MRTG to display monthly statistics of the iprb0
interface on a Solaris 10 host, I see unexpected four hour long
spikes of 2000-4000 B/s once in a while.

  Target[eth]:            2:public at localhost
  Directory[eth]:         network
  MaxBytes[eth]:          12500000
  kilo[eth]:              1024
  Title[eth]:             localhost : iprb0
  PageTop[eth]:           <H1>Traffic Analysis for iprb0</H1>
  Options[eth]:           growright,noinfo,integer,nopercent

I'm trying to find out what is causing this, and my questions is:

  What can one do using either SNMP, MRTG, or both to better
  learn about the monthly total traffic volume as would appear
  on the bill from a network provider?

Furthermore, is there a way to learn what the total traffic volume
was over the last n days? Is snmpget(1) useful for this, and if so
which MIB or OIDs?

Unfortunately the 'Max', 'Average', and 'Current' traffic meters of
MRTG don't do much to help me estimate my monthly traffic bill, and
from which virtual interface iprb0:n or even better which service
is generating the traffic.

Regards,
Brian