Please Help with your advice

I am setting up one A800 for t e r m i n a t i o n and adsl of 512/128 kbps. A modem/router will be used and the service provider gives only one fixed IP address. What can be done in this case? How many fixed IP’s do we need?

I have been suggested to use a Binatone ADSL 3000 which has 4 ports and the a mapping can be done to the gear.Is that fine?

Please help me out with your advice.

Thank you.