How to configure Fedora Core 1 as a gateway

by Thomas M. Andersen on Feburary 14, 2004

Everything below is done as the root user.

Edit the file /etc/sysctl.conf and on the line net.ipv4.ip_forward = 0, change 0 to 1.

	net.ipv4.ip_forward = 1

IP forwarding and Masquerading:
To flush old rules type this at the command line:

	$ iptables -F INPUT
	$ iptables -F OUTPUT
	$ iptables -F FORWARD
	$ iptables -t nat -F

The following commands will create new rules for your system.

	$ iptables -P INPUT ACCEPT
	$ iptables -P OUTPUT ACCEPT
	$ iptables -P FORWARD DROP
	$ iptables -A FORWARD -i eth0 -o eth1 -m state --state ESTABLISHED,RELATED -j ACCEPT
	$ iptables -A FORWARD -i eth1 -o eth0 -j ACCEPT
	$ iptables -A FORWARD -j LOG
	$ iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

You may have to switch eth0 and eth1 depending on your setup.

Save the iptables modifications by typing:

	$ service iptables save.

Done.