In this chapter, we covered redundancy and high availability. To this end, we discussed different types of load balancing and the basics of CARP. We then covered how to set up server load balancing in pfSense. We moved on to CARP configuration and provided two examples of CARP setups. The first was the conventional example of a CARP failover group with two firewalls - a master and a single backup. The second showed how it is possible to use CARP with three or more firewalls, and without much more configuration than would be necessary for the two firewall group. You may never have occasion to implement such a failover group, but it is encouraging to know that such enterprise-level redundancy is available to us.

We combined our knowledge of load balancing and CARP in an example that implemented server load balancing and a firewall failover group in a single network. Finally, we covered troubleshooting for redundancy and high availability, and acknowledged that the most common issues are virtual IP misconfiguration and neglecting to create firewall rules to allow traffic from the outside.

In the next chapter, we will cover a topic we held off in discussing in this chapter - gateway groups - as part of our coverage of multiple WANs. We will also expand on the example network we discussed in this chapter, and incorporate a multi-WAN setup into our network.