From: "jan gestre" <m0n0wall dot list at gmail dot com>

> guys,

> how do i block a particular client pc via its mac address? i'm not  using
> captive portal and clients obtain their ip addresses via the monowall's 
> dhcp
> server.

Under Services -> DHCP, at the bottom, add a static map to a black hole 
address.  For example, if you network is 192.168.1.0/24 make his MAC get 
10.1.1.1 and he will see nothing.  (However, if he gives himself a static IP 
address, it won't work)

                        Lee