Route only traffic from eth2

[enkil]

I hope this question is not too noob'ish, but I'm kinda confused when it comes to iptables.

Here's my network-layout:

eth0: 192.168.32.0/23
eth1: adsl (ppp0)
eth2: 172.16.0.0/24

I want to route traffic from 172.16.0.0/24 through ppp0. I'm kinda cautious with this, because I don't want to route traffic coming from 192.168.32.0/23.

Is it sufficient to do something like this (dunno if the syntax is right in the first place...)