Firewall live distro question

Hi,
I'm searching for a good firewall live distribution.
My goal is to renew my actual redhat 9 gateway machine (which features ssh,
named, iptables, dhcpd and little more) with a custom ad-hoc live
distribution.
I've googled around and some distro popped up, like Sentry Firewall,
Euronode and redWall, and i'm not sure which one to pick. Any one has
experience with any of these?
My requirements are:
- should be completely free (no commercial)
- easily customizable
- preferibly based on debian or fedora, with which i'm pretty confortable.

Thanks in advance,

MatB