I don't use Knoppix myself, but being based on Debian just like OZ on my Zaurus, there should be the file /etc/network/interfaces that looks something like this
Code:
auto lo
iface lo inet loopback
iface wlan0 inet dhcp
iface eth0 inet static
address 192.168.1.2
netmask 255.255.255.0
gateway 192.168.1.1
iface usbd0 inet static
address 192.168.129.201
netmask 255.255.255.0
gateway 192.168.129.200
(That should be fairly self-explanatory)