i need to know how i can forward all internet traffic from eth0 to eth1 (two nics on the same machine) using iptables. eth0 is connected to my router (internet connection) and eth1 is connected to a switch. eth1 will act as a gateway for my dhcp clients.

i'm not very familiar with iptables, but i know this can be done fairly easily. could someone show me how? thanks

Hi,
I had the same question / setup.
Try 'firestarter' from fs-security (google 'firestarter').
It worked fine for me when I couldn't figure out how to set this up by manually editing IP tables.
Rgds,
Alex

i would hate to install some software i don't really know much about just to get this to work. but then again, i really don't know much about iptables either. eventually i want to sit down and learn iptables but at the moment i am being bombarded with other projects. thats why i was hoping someone would just show me how to set up this simple rule with iptables.

i will take a look at firestarter it looks user friendly, thanks for your help.

if anyone else could show me how to set this up with iptables i would greatly appreciate it. thanks!

give these commands a try ..

#echo '1' > /proc/sys/net/ipv4/ip_forward
#iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
#iptables -A FORWARD -i eth1 -o eth0 -j ACCEPT
#iptables -A FORWARD -i eth0 -o eth1 -j ACCEPT

thanks pingu_penguin. i'll try that out. unfortunately i'm in the middle of another "IT emergency" right now so i'm currently busy with something else. i will post with results as soon as i get the chance.

ok after a lot of trial and error, i figured out i really don't need iptables rules. all i needed was the first line that pingu_penguin provided:

and of course a correct configuration of dhcpd.conf since my clients are dhcp clients.

btw, i am running ubuntu 7.10

thanks for everyone's help