The Gentoo installer lacks methods of connectivity to the internet. It currently only supports manual ethernet configuration aswell as dhcp configuration as far as I know. It should really also support PPP and possibly ISDN as they are two popular methods of connection to the internet.
Shouldn't be too hard on the CD .. I'd suggest WVDIAL for PPP and some nice ISDN setup shouldn't be too hard to find :)
wvdial and pppd are now on the -r15 CD. Not so sure about ISDN; I can't do that until I get more info about what's required.