兩套 Free firewall / NAT / VPN server

比較推薦:
http://www.pfsense.com/

另一套:
http://m0n0.ch/wall/

m0n0wall is probably the first UNIX system that has its boot-time configuration done with PHP, rather than the usual shell scripts, and that has the entire system configuration stored in XML format.

—> 可以看一下他怎麼寫這個的 “boot-time configuration”