firewall distros

[Jeremy Miller]

I am getting ready to turn the P3 under my desk into a
firewall/router. There are many distros like that available and I
wanted to know if anyone could recomend something. My only
requirements are that it can assign IP addresses based on mac
addresses (I think this is available with dnsmasq), have dns cacheing
built in, and have some kind of interface (web prefered but ncurses or
similar is OK). Nothing against BSD but I would prefer a Linux based
distro only because I am farmiliar with it.

Thanks in advance.