I'm trying to set up Routing and Remote Access on Windows Server 2008 R2, I have a network connection that I want to share the internet from to another private network.

The server has two NICs which are configured as follows:

External NIC (Dynamically assigned by ISP)
IP:10.175.4.150
Subnet:255.255.192.0
Gateway:10.175.0.1
DNS:10.175.0.1

Internal NIC
IP:172.16.254.1
Subnet:255.255.255.0
Gateway:None
DNS:None

I have set the external NIC to be the public interface and enabled NAT on it in the RRAS MMC and set the internal NIC to be a private interface. I have also set up the DNS forwarding or whatever it is in the NAT section.

From a client (IP:172.16.254.2) I can ping the server and access files on it, when I try to browse the web with the default gateway set to the internal NIC ip I end up getting a 404 page which is returned from the ISPs default gateway. I'm guessing it's something to do with the double NAT possibly. Trying to ping the ISPs default gateway from a private network client just times out as does accessing it directly.

I've disabled and reconfigured RRAS multiple times and that doesn't seem to have made a difference, so can anyone tell me what I'm doing wrong?

Thanks.