To turn a linux box with two network interfaces into a NAT router with the most basic functions, four separate changes are required. This is more complicated than it needs to be. For future reference:

1. Enable packet forwarding in the “registry”:
Edit /etc/sysctl.conf to add
net/ipv4/ip_forward=1 then
> sysctl -p /etc/sysctl.conf

2. Set address sharing for outbound traffic and poke holes in the firewall:
Assume eth0 is the WAN-facing interface and eth1 is the LAN-facing interface, then
> iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
> iptables -t filter -A FORWARD -i eth1 -o eth0 -j ACCEPT
> iptables -t filter -A FORWARD -i eth0 -o eth1 -m state –state ESTABLISHED,RELATED -j ACCEPT
> /etc/init.d/iptables save active
> /etc/init.d/iptables restart
Turn on the iptables service in sysvconfig

3. Enable automatic serving of dynamic LAN IP’s:
Assume 10.0.0.x is the LAN-side subnet and 192.168.0.1 is the WAN-side DNS server or gateway, then
Edit /etc/dhcp3/dhcpd.conf to add, e.g.
subnet 10.0.0.0 netmask 255.255.255.0 {
     range 10.0.0.2 10.0.0.10;
     option routers 10.0.0.1;
     option domain-name-servers 192.168.0.1
}
> /etc/init.d/dhcp3-server restart

4. Set the LAN-facing interface to be on the LAN-side subnet:
Assume 10.0.0.1 is the LAN-side address of connection sharing machine, then
Edit /etc/network/interfaces to add
auto eth1
iface eth1 inet static
     address 10.0.0.1
     netmask 255.255.255.0
     gateway 192.168.0.1
> /etc/init.d/networking restart

Comments(0)

link.

Edit: All right, the author deleted the page, but Google says it started out like this:

Screw NBC Watch CBC/CBUT for 2008 Olympic Coverage28 Jun 2008 by teamstrannon

For Americans the road to our 2008 Beijing Olympics will be on a 12-15 hour delay. That is NBC’s best attempt to give us timely Olympics coverage in our high-end technology era. You’d think it was still 1950. Yep folks, that’s all we’re …

Basically the Canadian network CBC (and local affiliate CBUT Vancouver) had Olympics on live coverage, so people in select markets in the US served by cable that picks up that Canadian channel could bypass NBC completely. It was better editorial coverage anyway.

Comments(0)