Reference Guide

11-8 User’s Reference Guide
Advanced configuration – Server Lists and Dynamic NAT
You use the advanced NAT feature sets by first defining a series of mapping rules and then grouping them into
a list. There are two kinds of lists -- map lists, made up of dynamic, PAT and static mapping rules, and server
lists, a list of internal services to be presented to the external world. Creating these lists is a four-step process:
1. Define the public range of addresses that external computers should use to get to the NAT internal
machines. These are the addresses that someone on the Internet would see.
2. Create a List name that will act as a rule or server holder.
3. Create a map or rule that specifies the internal range of NATed addresses and the external range they are
to be associated with.
4. Associate the Map or Server List to your WAN interface via a Connection Profile or the Default Profile.
The three NAT features all operate completely independently of each other, although they can be used
simultaneously on the same Connection Profile.
You can configure a simple 1-to-many PAT (often referred to simply as NAT) mapping using Easy Setup. More
complex setups require configuration using the Network Address Translation item on the IP Setup screen.
An example MultiNAT configuration at the end of this chapter describes some applications for these features.
See the MultiNAT Configuration Example on page 11-30.
In order to configure the router to make servers on your LAN visible to the Internet, you use advanced features
in the System Configuration screens, described in IP setup on page 11-9.
Note: There is no implicit binding between the WAN IP interface address and NAT, as in earlier firmware
versions, so you cannot disallow configuration of NAT simply because the interface is numbered or disallow
configuration of the addressing type (numbered or unnumbered) simply because NAT is enabled.
If the router has a numbered interface, then it is addressable by the IP address. In firmware versions earlier
than 4.4, when NAT was enabled the interface would be marked unnumbered and the IP address subsumed by
NAT. However, NAT would allow traffic directed to that IP address to be delivered to the router. This effectively
made the interface a numbered interface. MultiNAT adds the option of true unnumbered NAT. Traffic delivered
to the router on an unnumbered interface which cannot be processed by NAT is dropped.