Hi carl ,
You should assign ip address to an interface or you can use ip unnumbered for particular interface.Interface willn't work without ip address.
The maximum bandwith for ADSL connections are up to 8 Mbps downstream and up to 835 Kbps
upstream.
The speed is not dependent of router configuration but it is solely determined by the ISP.
The speed is going to depend also on a series of factors such as distance, quality of the
line, and noise, among the most import ones.
Thanks,
satish