ZyXEL Communications 2 Plus User Manual

Chapter 17 Network Address Translation (NAT)

ZyWALL 2 Plus User’s Guide

The following table describes the labels in this screen.  

A port forwarding set is a list of inside (behind NAT on the LAN) servers, for example, web or 
FTP, that you can make visible to the outside world even though NAT makes your whole 
inside network appear as a single computer to the outside world. 
You may enter a single port number or a range of port numbers to be forwarded, and the local 
IP address of the desired server. The port number identifies a service; for example, web 
service is on port 80 and FTP on port 21. In some cases, such as for unknown services or 
where one server can support more than one service (for example both FTP and web service), 
it might be better to specify a range of port numbers. You can allocate a server IP address that 
corresponds to a port or a range of ports.
Many residential broadband ISP accounts do not allow you to run any server processes (such 
as a Web or FTP server) from your location. Your ISP may periodically check for servers and 
may suspend your account if it discovers any active services at your location. If you are 
unsure, refer to your ISP.

In addition to the servers for specified services, NAT supports a default server IP address. A 
default server receives packets from ports that are not specified in this screen.

Table 97   ADVANCED > NAT > Address Mapping > Edit

Type

Choose the port mapping type from one of the following. 
1. One-to-One: One-to-One mode maps one local IP address to one global IP 

address. Note that port numbers do not change for One-to-One NAT mapping 

type.

2. Many-to-One: Many-to-One mode maps multiple local IP addresses to one 

global IP address. This is equivalent to SUA (i.e., PAT, port address translation), 

ZyXEL's Single User Account feature. 

3. Many-to-Many Overload: Many-to-Many Overload mode maps multiple local 

IP addresses to shared global IP addresses. 

4. Many One-to-One: Many One-to-One mode maps each local IP address to 

unique global IP addresses. 

5. Server: This type allows you to specify inside servers of different services 

behind the NAT to be accessible to the outside world.

Local Start IP

This is the starting Inside Local IP Address (ILA). Local IP addresses are N/A for 

Server port mapping.

Local End IP

This is the end Inside Local IP Address (ILA). If your rule is for all local IP 

addresses, then enter 0.0.0.0 as the Local Start IP address and 255.255.255.255 

as the Local End IP address. 
This field is N/A for One-to-One and Server mapping types.

Global Start IP

This is the starting Inside Global IP Address (IGA). Enter 0.0.0.0 here if you have 

a dynamic IP address from your ISP. 

Global End IP

This is the ending Inside Global IP Address (IGA). This field is N/A for One-to-

One, Many-to-One and Server mapping types.

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