Nat; Chapter 18 Nat; Nat Overview; What You Can Do In This Chapter - ZyXEL Communications ISG50-ISDN User Manual

Integrated service gateway

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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 ISG50 available outside the private

network. If the ISG50 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 212 Multiple Servers Behind NAT Example

Use the NAT screens (see

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

NAT is also known as virtual server, port forwarding, or port translation.

Finding Out More

Section 6.6.9 on page 100

Section 18.3 on page 328

Section 7.9.2 on page 126

from the WAN to the LAN.

ISG50 User's Guide

Section 18.2 on page

324) to view and manage the list of NAT rules and

for related information on these screens.

for technical background information related to these screens.

for an example of how to configure NAT to allow H.323 traffic

NAT