We have kernel support for IPv6 in Centos, but not stateful firewall support. That requires at least the 2.6.20 kernel, which means Fedora Core 6 or some other Linux distro. None of the various free Linux firewalls have IPv6 support. Supposedly FWBuilder can manage Netfilters for a Linux Kernel, but that seems to be the extent of it. More sad facts as I uncover them.....