Linux Firewalls, Third Edition

Summary

This chapter covered Network Address Translation. Initially, three basic types of NAT were described. NAT's original purpose, what it is used for today, and its advantages and disadvantages were discussed as well.

In iptables, NAT features are accessed through the nat table and that table's chains rather than through the filter table and the FORWARD chain. The implications of packet flow through the operating system, and the differences between what address rules match against on the FORWARD chain versus on the nat chains, were discussed.

iptables implements both source NAT and destination NAT. Source NAT is divided into two subcategories, SNAT and MASQUERADE. SNAT is regular source address translation. MASQUERADE is a specialized implementation ...