ZyXEL Communications 1000 Manual De Usuario

ZyWALL USG 1000 User’s Guide

NAT (Network Address Translation - NAT, RFC 1631) is the translation of the IP 
address of a host in a packet. For example, the source address of an outgoing 
packet, used within one network is changed to a different IP address known within 
another network. Use Network Address Translation (NAT) to make computers on a 
private network behind the ZyWALL available outside the private network. If the 
ZyWALL has only one public IP address, you can make the computers in the 
private network available by using ports to forward packets to the appropriate 
private IP address. 

Suppose you want to assign ports 21-25 to one FTP, Telnet and SMTP server (A in 
the example), port 80 to another (B in the example) and assign a default server IP 
address of 192.168.1.35 to a third (C in the example). You assign the LAN IP 
addresses and the ISP assigns the WAN IP address. The NAT network appears as a 
single host on the Internet.

Figure 290   Multiple Servers Behind NAT Example

Use the NAT screens (see 

) to view and manage the list 

of NAT rules and see their configuration details. You can also create new NAT rules 
and edit or delete existing ones.