I have set up 2 network cards, each with an individual IP address.
I also have a script that forwards all incoming traffic on "port a" to "port b".
I now want the script to port forward data from ppp0, port a ---->to------> eth0, port b.
How do I define whether it's ppp0 or eth0 I want the data to come from and go to?
Data can only come from ppp0 (3G card)
AND data can only go to LAN through eth0.
Understand? any clues?