PsygNAT is a free firewall and NAT router tool for i386 which boots off on a single floppy. It is based on the OpenBSD kernel and therefore, uses pf as its native ruleset management.
PsygNAT contains the necessary tools in configuring a simple NAT router, a stateful (and transparent) firewall, or a bandwidth limiter via ALTQ. It supports both static and dynamic client setup. It also includes mg, an emacs-like text editor, which can be used to write firewall and network address translation rules.