Juniper SRX Series

Chapter 9. Network Address Translation

Network Address Translation (NAT) is a fascinating and storied technology in computer networks. Perhaps more than any other network technology, NAT has found itself in the corner of many different use cases. Originally developed to extend the life of the IPv4 protocol after the exhaustion of the 4 billion public IP addresses (because an IPv4 address has 32 bits, and thus there are 2³² available addresses). From its original purpose it gained wide popularity as a security technology to hide IP addresses and prevent inbound network connections, and now has seen many other uses. Today, it is being used extensively by service providers for carrier-grade NAT, by network administrators worldwide for IPv4 to IPv6 translation, and even on virtual machine hosts. Who would have seen a single physical computer needing to leverage NAT 15 years ago? Although it certainly isn’t the sexiest technology discussed in this book, it is necessary in most contemporary networks and can provide other benefits to provide a transparent network experience to users on their networks.

In this chapter, we focus on the core NAT technologies offered by the SRX. We start with a discussion of how NAT is processed on the SRX, with a thorough look at how it is implemented and configured from an administrative perspective. We delve into each of the different core NAT technologies supported on the SRX, including source, static, and destination NAT. We also examine IPv6 with NAT, ...