Working through all the examples in this chapter will require at least three working pfSense systems, either in a real-world or virtualized environment. If you are implementing a CARP setup on your network and plan to have two or more redundant firewalls, be aware that this means two or more WAN interfaces, which will require either additional public internet addresses from your ISP, or a router to interconnect the WAN interfaces with your modem (or whatever internet connectivity device you use).