I configured a double nat using another firmware, but it's not clear to me how to do it in Tomato.
INTERNET <-> Tomato-shibby with LAN 172.18.1.0 subnet <->second router WAN 172.18.1.11 with LAN 192.168.1.0 <->192.168.1.2 client
The 192.168.1.2 client has a default gw 192.168.1.1
There is a static route in the Tomato-shibby-router that sends all 192.168.1.0 traffic to 172.18.1.11. But still no Internet on 192.168.1.0. I can't nslookup google.com from 192.168.1.0 subnet. It seems like maybe I'm missing something.
** server can't find google.com: REFUSED