Iptables postrouting
# /sbin/iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE # /sbin/iptables -A FORWARD -i eth0 -o eth1 -m state --state RELATED,ESTABLISHED -j ACCEPT # /sbin/iptables -A FORWARD -i eth1 -o eth0 -j ACCEPT You should now be NATing. You can test this by pinging an external address from one of your internal hosts.