Indispensable book for building invisible firewalls (bridges), packet filtering, NAT and routing devices. Rock solid guide! Includes the basics for beginners such as hardening the OS, (though with OpenBSD it's a short list) and avoiding gateway IP configuration mistakes. Saved me DAYS scouring the manual pages or web. Covers advanced topics such as firewall/network designs, packet filtering, allowing FTP, patching, secure levels, creating maintenance users, anti-spoofing, automated firewalls, bandwidth shaping and load balancing, logging and analysis, authpf, firewall testing and management AND did I mention using spamd to filter spam? Obviously this book has not had any bench time in my office. Simply the best way to get up and running on OpenBSD networking. Note, you can support OpenBSD and still purchase from Amazon by going through the link: http://www.openbsd.org/books.html