Redundant OpenBSD Firewalls – a 6 part guide that describes how to configure two pieces of hardware running OpenBSD to create a redundant pair of firewalls with instant failover which provides DNS, DHCP, and NTP services.

OpenBSD NTP Server With GPS Time Sensor – Add an inexpensive USB GPS receiver to your OpenBSD time server to increase resiliance and ensure accurate time when internet connectivity is not available.