Chapter 4. Network Address Translation

This chapter covers the following key topics:

• Operation of NAT ” This section discusses the basics of network address translation, including fundamental concepts and terminology, and typical NAT applications.

• NAT Issues ” This section examines some potential problems that you might encounter with NAT. Solutions to many of the problems, either through Cisco IOS Software functionality or through design techniques, are identified.

• Configuring NAT ” This section presents case studies demonstrating how Cisco IOS Software is configured to perform typical NAT functions.

• Troubleshooting NAT ” This section examines various methods and tools for troubleshooting Cisco NAT.

Network address translation (NAT) is a function by which IP addresses within a packet are replaced with different IP addresses. This function is most commonly performed by either routers or firewalls. This chapter, of course, focuses on NAT within routers.

NOTE

The acronym NAT is used interchangeably to mean network address translation and network address translator (software that runs the NAT function).