I've set up SSH on the Tomato firmware on an Asus N10, via port 22 with key authentication.

I've tested the keys by connecting with putty directly to the router when connected to its network. That works OK. But this router is behind a Belkin (F5D7632-4) router which also acts as modem and when I try to connect through with the (dynamic) public IP it times out. I'm guessing it's something to do with the NAT?

My putty settings are taken from various online tutorials, but it's set up for port 22, with the correct key as mentioned. The Belkin router has port forwarding to the Asus (192.168.2.3) for port 22 TCP and UDP set up.

It's now tough to see what to do in order to connect to the Asus router with an external IP - if it's even possible. Ideally I would have liked to have only needed to use the Asus router, but as it doesn't act as a modem, I need to connect it to the Belkin to use Tomato's features. Perhaps there's a solution here too?

Network: Internet -> Belkin modem/router -> Asus router (Tomato SSH) -> Devices