packet forwarding

[Andrew Critchlow]

Hello everyone,
 
I am trying to set up a debian proxy such as this:
 
USER--------DEBIAN--------INTERNET
 
The debian box will have two network cards.
 
How can I set up the debian box to forward packets between the two networks? Do 
I have to set up packet forwarding by adding:
net.ipv4.ip_forward=1
into /etc/sysctl.conf
 
?
 
 
 
Many thanks
 
andrew.