Here we give examples for three different sorts of network: a simple home NAT device with no services, a small office with a restricted-capacity web server, and a 3-tier architecture application server farm using load balancing. While these examples are written to be different than those complete examples provided by the OpenBSD Project and related resources, they may well create some similar examples by the time you read this.
These examples are written to be plugged into /etc/pf.conf. All you need to do to use them is enable PF in /etc/rc.conf, and enable packet forwarding.
As typing in examples from a book is quite an annoyance, text files of these example configuration files are available from http://www.AbsoluteOpenBSD.org. Be sure to check there for any updates!