> Using ipchains, is it possible to implement authentication for a group > of users, here the teachers? No. It is not possible to implement authentication given currently-deployed DHCP technology, period. If you want students and teachers to wind up in different subnets on a shared network, you have to use classes and subclasses to do it. Easiest to put the teachers' computers in subclasses. I believe there is an example of this in the DHCP Handbook, but I don't have it, ... well, ... handy... So I can't verify that. :'} _MelloN_ - : send the line "unsubscribe linux-net" in the body of a message to majordomo@vger.kernel.org