[TriLUG] help with mrtg

[Brian A. Henning]

Hi Everyone,
  I just noticed, while staring idly at the output of top, that mrtg
occasionally chews up a chunk of processor time.  Having dealt with certain
ISP's mrtg, I thought, "Hey, I know what mrtg is!" and set about trying to
find out how to view its statistics.

Egad.

Okay, so I am a complete newb in terms of SNMP and its related, um, things..
(Case in point?)  I tried looking through the mrtg config details, and made
no sense of it.  About the only thing I could figure out by examining the
mrtg-related files on my system is that it's not configured to actually *do*
anything.

Problem is, I have no idea what to tell it to do, nor what to tell it to do
it do.  It looks like mrtg queries data from SNMP-enabled routing hardware.
Well, I don't have any standalone routing hardware; the same linux box
handles the little bit of NATting/routing I need.  Here's what I'd like to
know, if there is someone patient enough to point me through it:

- How to "turn on" SNMP so that my machine logs traffic statistics (please
correct my jargon; as mentioned, I really don't know much of what I'm
talking about here).  Here's some potentially useful information about my
setup (RH7.3, kernel 2.4.20-20.7):
  - I'm routing / NATting with iptables.
  - tc is doing some minor bandwidth limiting
  - for discussion purposes, my internal iface is eth0, my external iface is
eth1
  - what else do I need to know?

- How to tell mrtg to get its stats from the localhost, instead of some
external appliance

Is there hope for me?

Thanks in advance,
~Brian