I've recently come across a couple of ADSL modems with NAT enabled. In both cases there are wireless routers involved too so the computers are effectively "double-NATted". I'm surprised the modems are using NAT - I thought the usual scenario was that the ISP allows for one IP, and if you have more than one device get a router. That's what TCL does. Quite what the need for NAT is in the modem I don't know.
Anyway, my question is: does anyone know if this is normal in NZ? How about with ADSL (or other) connections overseas?
Some background: I've developed a couple of products that make services available on the net; they're targeted at your average home or small office user. I use UPnP and NAT-PMP to open a port in the router for incoming connections. Great, usually, but this won't get through two layers of NAT of course.
Obviously there are ways around this with a bit of configuration - make the modem DMZ to the router, or put the router in bridge mode (the first being more useful because the modems seem not to do UPnP) - but I'm trying to take the burden of configuration away from the user. This NAT-behind-NAT scenario has me a little worried, so any advice as to how common it is would be great.