The configuration looks good. What is the ip address on eth0/0 and how is any forwarding to that address done on your modem?
You mention that it has a dhcp reservation, so I am wondering if this is actually an rfc1918 private address that is not internet routable. Which would require a forwarding setup on the modem to this address too.
Or do you have bridge mode setup on the modem and get an actual public address?