Cisco WAN :: Assign Static IP To WAG320N Using PPPoA

with my broadband internet I received a range of 5 IP addresses from BT. I would like to assign one of them to the modem, in order to reach the modem from the outside using that IP.,Is this theoretically possible at all?,Is the WAG320N supporting static IP addresses with PPPoA at all?,When I select PPPoA as the encapsulation on the Setup/Basic setup tab, I cannot enter an IP address on that tab. I tried using the Setup/Ethernet tab, but selecting ""Use as a WAN port", "Static IP", inserting the IP and clicking on "save" result in a cut of the internet connection.