Introduction

Address translation has become a staple of enterprise networking, and its development has allowed users of the Internet to forestall its collapse under the weight of the explosion of Internet devices and the basic limitation of IPv4 addresses.

Network Address Translation (NAT) has become one of the most common firewall functions, and its simplicity has allowed the number of devices that can use the Internet to expand exponentially. It is the one key function that has provided home users with the capability to allow every member of a household to have his or her own computer and share a single Internet connection from a broadband ISP. In addition, its implicit nature to isolate individual devices from the general Internet public provides a very powerful firewall against malicious outsiders.

In the corporate environment, NAT offers the same benefits and, as implemented by the SonicWALL SonicOS, extends the features to allow network administrators to carefully control the inbound and outbound traffic they need to support.

The SonicOS software offers the network administrator the ability to perform IP address translations, IP protocol or port translations, and a combination of both at the same time. These translations can be performed in a number of ways:

• From a single address to a single address One-to-One NAT

• From a single address to multiple addresses One-to-Many NAT

• From multiple addresses to a single address Many-to-One NAT

• From multiple addresses to a pool of other multiple addresses Many-to-Many NAT

In this chapter, we discuss the uses of these variations and how...