Telus just updated my DSL modem to the T3200M. Having difficulty port forwarding and noticed that my new modems IP address is different than my public IP address (via What's My IP or Dynamic DNS Service). I always thought the modem IP address was the same as the public IP. To what address do I route to connect to an device behind the router?? Can you successfully port forward with the T3200M?
My router, under WAN Connection Status, indicates my modem IP address is 100.XXX.XXX.XXX. The website you provided and the normal 'what's my IP?' search, and the DNS reporting from my connected IP cameras suggest my public IP address is 209.XXX.XXX.XXX. I'm no IT expert but that's the first time I've seen this.
If your public IP address is different than your router WAN IP address then it's due to Carrier Grade NAT. We are running out of public IP4 addresses so carriers need to put a shared layer of IP4 addresses between some customers and the public Internet. This is why port forwarding at your router doesn't work. You would need an additional port forward from the true public IP at the carrier level to your WAN IP which of course we can't do.
There are many discussions on this in the Neighborhood: