# Set up IP FORWARDing and Masquerading
iptables –table nat –append POSTROUTING –out-interface eth1 -j MASQUERADE
iptables –append FORWARD –in-interface eth0 -j ACCEPT

echo 1 > /proc/sys/net/ipv4/ip_forward

This is not enough in FC4. You should also enable trusted and masquarade for the LAN interface in SELinux.