Chapter 10 Network Address Translation

 

 

 

 

Table 45 Network > NAT > Port Triggering (continued)

 

LABEL

DESCRIPTION

 

Start Related

Type a Starting port number that is related to the open protocol.

 

Port

 

 

 

 

 

End Related

Type a Ending port number that is related to the open protocol.

 

Port

 

 

 

 

 

Open Protocol

The open protocol is the protocol (UDP, TCP or UDP/TCP) that causes (or triggers) the

 

 

NBG-418N v2 to record the IP address of the LAN computer that sent the traffic to a

 

 

server on the WAN.

 

 

 

 

Apply

Click Apply to save your changes back to the NBG-418N v2.

 

 

 

 

Cancel

Click Cancel to begin configuring this screen afresh.

 

 

 

10.6 Technical Reference

The following section contains additional technical information about the NBG-418N v2 features described in this chapter.

10.6.1 NAT Port Forwarding: Services and Port Numbers

A port forwarding set is a list of inside (behind NAT on the LAN) servers, for example, web or FTP, that you can make accessible to the outside world even though NAT makes your whole inside network appear as a single machine to the outside world.

Use the Application screen to forward incoming service requests to the server(s) on your local network. 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.

In addition to the servers for specified services, NAT supports a default server. A service request that does not have a server explicitly designated for it is forwarded to the default server. If the default is not defined, the service request is simply discarded.

Note: 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.

10.6.2 NAT 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.

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