It is difficult to use ADSL on Knoppix 3.6 without special configur.
You can do like this.
1.Open a terminal.
2.su
3.Type the following: Ifconfig eth0 down
4.MENU--netcard configur
5.USE the following:
IP address for eth0:192.168.0.0
NETMASK 255.255.255.0
Broadcast 192.168.0.255
Gateway 0.0.0.0
6.MENU-adsl configur
7.Enjoy it!