Creating NAT rules

Unless you are one of the lucky few organizations that were able to get their very own A (/8) or B (/16) class subnets, your internal network segments will most likely be made up of one or several of the well-known RFC1918 private IP address allocations: 10.0.0.0/8, 172.16.0.0/12, or 192.168.0.0/16. NAT is needed in order for your hosts to be able to reach the internet and your customers and partners to reach publicly available resources hosted in your data center. NAT rules can be configured through Policies | NAT.

For this section, keep the following interface setup in mind:

Figure 3.42: Interface zone and IP configuration

Address translation comes in different flavors depending on the direction and purpose, each with its own nuances. Let’s first review inbound NAT.

Inbound NAT

For inbound NAT, it is important to remember that the firewall is zone-based and that the source and destination zones are determined before the NAT policy...