Chapter 8 Network Address Translation (NAT)

"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.

Default Server IP Address

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.

"If you do not assign a Default Server IP address, the ZyXEL Device discards all packets received for ports that are not specified here or in the remote management setup.

Configuring Servers Behind Port Forwarding (Example)

Let's say 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 71 Multiple Servers Behind NAT Example

A=192.168.1.33 LAN

 

WAN

B=192.168.1.34

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

192.168.1.1

C=192.168.1.35 D=192.168.1.36

IP Address assigned by ISP

8.3.1 Configuring the Port Forwarding Screen

Click Network > NAT > Port Forwarding to open the following screen.

See Appendix E on page 373 for port numbers commonly used for particular services.

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P-660HN-F1 User’s Guide