Answer by Daniele Santi for Can't route into WAN with IPCop Router

rIn your NAT configuration, I don't see a MASQUERADE target.

I have no experience with IPCop configuration, and it's been a while since I configured NAT with iptables, but can you try these lines in your shell?

/sbin/iptables -t nat -A POSTROUTING -o eth1 -j MASQUERADE/sbin/iptables -A FORWARD -i eth1 -o eth0 -m state --state RELATED,ESTABLISHED -j ACCEPT/sbin/iptables -A FORWARD -i eth0 -o eth1 -j ACCEPT

also check if

cat /proc/sys/net/ipv4/ip_forward

returns 1. And if not, do a

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

If after these commands it works, you'll have to check your IPCop configuration on how to enable them.