I have two mchaines which one is pysically connected to the internet, the RHEL5 machine, and a second machine that is connected to the first via a crossover cable. The RHEL5 has two NIC cards. eth0 is connected to the internet via a DHCP server. eth1 has a static address of 192.168.1.1. The second machine that I would like to have internet access to has a single NIC and a static address of 192.168.1.2 with a gateway set to 192.168.1.1. Would I just ahve to run the following command on the RHEL5 machine to give internet access:

iptables -t nat -A POSTROUTING -o eth1 -j MASQUERADE

TIA,
Keith

You also need to run this command to enable ip forwarding as well.
echo "1" > /proc/sys/net/ipv4/ip_forward
Then the one you mention.
/sbin/iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

You can place both of those commands in /etc/rc.local so they are ran on boot. Be sure to use the full path of each command.

Now a few things to configure. Set the eth0 as the Internet wan connection like you mention getting the DHCP IP. Now with the eth1 set the IP and Subnet info. Do Not Set a gateway on this nic.

I presume you are still going to leave current iptables service enabled on the machine. If not I would do the following.

I would perform a bit better firewalling if any ports are to be opened on the RHEL5 Internet router box. I would goto here and answer the questions to configure a very secure and simply router script and place this script to be runned in /etc/rc.local. You will need to disable the RHEL5 default firewall if you go that route.