ZyXEL ZyWALL USG 2000 User Guide - Page 387

CHAPTER 19 NAT 19.1 NAT Overview 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 19.1.1 What You Can Do in this Chapter Use the NAT screens (see Section 19.2 on page 388) 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. ZyWALL USG 2000 User's Guide 387