Knoppix uses pump and not dhclient. This is one of the differences between Debian Etch and Knoppix. pump performs about the same functions as dhclient. I don't use it very often, but the options are all given in the man pump. To see what your network settings are, type pump -s. pump -i eth1 will make eth1 try to get an ip from your dhcp.

You can also try using the network card configuration option which is at Knoppix menu (penguin) -> network/internet -> network card configuration.