High availability firewalls with OpenBSD, pf and CARP

One can now inexpensively build a fault tolerant firewall cluster that removes any single point of failure in the security policy enforcement points at your security zone boundaries. Synchronous firewall state table updates and an open source version of virtual router redundancy protocol (CARP) gives the ability to seamlessly insert or remove firewalls from a cluster. No more patching firewalls at 2am hoping for the best (or not patching because it’s too hard).