[mrtg] separating WAN traffic from LAN traffic

[Steve Shipway]

> I have an interface for which I'd like to graph only the traffic to and
> from the WAN, and ignore the traffic to and from the LAN. 
...
> Is there some simple way to graph just the WAN traffic, given my
> constraints?

I do this on my home network gateway router.  The way I achieve it is by
using the Linux IPTables rules and then having a custom plug-in for MRTG to
extract the packet counts from the matching rules.  It requires a couple of
extra rules in the IPTables (actually, I create a special logging chain and
redirect external traffic through it) and a custom MRTG plug-in to query the
iptables status output.

Of course, this requires the server in question to be running Linux.
Otherwise, you'll need to see if your server has similar features, or use an
RMAN probe or sniffer.

If you're using Linux and you'd like more details let me know.
Alternatively, full instructions on doing this with iptables are given in
Chapter 7 of the 'Using MRTG with RRDtool and Routers2' book - see
http://www.steveshipway.org/book to get a copy (sorry for the advertising)

Steve

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