Address Translation; Nat - D-Link NetDefend DFL-210 User Manual

Chapter 7. Address Translation
This chapter describes NetDefendOS address translation capabilities.
• NAT, page 283
• NAT Pools, page 288
• SAT, page 291
The ability of NetDefendOS to change the IP address of packets as they pass through the D-Link
Firewall is known as address translation.
The ability to transform one IP address to another can have many benefits. Two of the most
important are:
• Private IP addresses can be used on a protected network where protected hosts need to have
access to the public Internet. There may also be servers with private IP addresses that need to be
accessible from the public Internet.
• Security is increased by making it more difficult for intruders to understand the topology of the
protected network. Address translation hides internal IP addresses which means that an attack
coming from the "outside" is much more difficult.
Types of Translation
NetDefendOS supports two types of translation:
• Dynamic Network Address Translation (NAT).
• Static Address Translation (SAT).
Both types of translation are policy-based in NetDefendOS, which means that they can be applied to
specific traffic based on the source/destination network/interface as well as based on the type of
protocol. Two types of NetDefendOS IP rules, NAT rules and SAT rules, are used to configure

address translation.

This section describes and provides examples of configuring NAT and SAT rules.

7.1. NAT

Dynamic Network Address Translation (NAT) provides a mechanism for translating original source
IP addresses to a different address. Outgoing packets then appear to come from a different IP
address and incoming packets back to that address have their IP address translated back to the
original IP address.
NAT can have two important benefits:
• The IP addresses of individual clients and hosts can be "hidden" behind the firewall's IP address.
• Only the firewall needs a public IP address for public Internet access. Hosts and networks
behind the firewall can be allocated private IP addresses but can still have access to the public
Internet through the public IP address.
NAT Provides many-to-one IP Address Translation
283