I was hoping that someone would be able to help me write some iptables rules to create a nat pool on my router. The firewall/router is Redhat 9.

I'll try to describe my setup. I have one device (Windows - stop laughing) functioning as a gateway/proxy with 2 NICs. The internal NIC is 10.14.0.3 and serves up a DHCP pool from 10.14.0.100-250. The other NIC is 10.15.0.3 and connects directly to the firewall/router. The firewall/router has 2 NICs as well. One is 10.15.0.1 and the other is a public address (206.x.x.x). Right now, the gateway is setup as a transparent proxy so it has it's own nat pool. We would like to turn the transparent proxy off and create the nat pool rules on the firewall/router. I know that we need to specify that any traffic headed for the 10.14 network from 206 should be sent to 10.15. Can someone explain to me how this is done with iptables?

Thanks

You will need to know some of the other rules and when to use them,
so I suggest reading this iptables tutorial

It's big but covers nearly everything, there are scripts at the end..