Regardless of your deployment scenario, there is a good chance you will want to utilize pfSense to filter network traffic, as having control over traffic entering and leaving our networks is one of the main functions of a pfSense firewall. The primary mechanism that we employ for filtering traffic is the creation of firewall rules, and we will detail the process in this chapter. We will also introduce some real-world examples of using pfSense to selectively block traffic, or to allow certain traffic only during certain hours via scheduling.

Another component that we sometimes use in filtering traffic is Network Address Translation (NAT). NAT played an important role in forestalling IPv4 address exhaustion, as it enabled a network to have one IP address for the public internet and many private addresses, with NAT directing traffic in both directions to the correct destination. Although NAT is likely to diminish in importance with the continuing migration to IPv6, it is nonetheless likely to be a component of our networks in the near future, and will be covered in this chapter.

The following topics will be covered in this chapter:

• Firewall fundamentals
• Firewall best practices
• Creating firewall rules
• Scheduling
• Aliases and virtual IPs
• Network Address Translation (NAT)
• Troubleshooting