I have an internet connection over ADSL through a Linksys SOHO router. The external IP address is dynamic. The linksys internal IP address is 192.168.200.1
Behind Linksys router, there is an ISA server with two LAN interfaces. The external interface is connected to the Linksys router with IP address 192.168.200.2. The internal interface is connected to the office network and has an IP address 192.168.0.4
There are many services in the internal network 192.168.0.0 which should be published to the Internet (Like SMTP 25, IAX2 4569, RDP 3389....)
The linksys router doesn't accept port forwarding to any destination outside it's local network (192.168.200.0).
I have tried to forward some port to the ISA 192.168.200.2, and then republish the desired port through ISA, but it didn't work.
Can anybody give me a solution when there are two NAT firewalls behind each other?