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Reference Manual for the Model DG824M Wireless ADSL Modem Gateway
Protecting Your Network 4-7
Inbound Rules (Port Forwarding)
Because the DG824M uses Network Address Translation (NAT), your network presents only one
IP address to the Internet, and outside users cannot directly address any of your local computers.
However, by defining an inbound rule you can make a local server (for example, a web server or
game server) visible and available to the Internet. The rule tells the gateway to direct inbound
traffic for a particular service to one local server based on the destination port number. This is also
known as port forwarding.
Remember that allowing inbound services opens holes in your firewall. Only enable those ports
that are necessary for your network. Following are two application examples of inbound rules:
Inbound Rule Example: A Local Public Web Server
If you host a public web server on your local network, you can define a rule to allow inbound web
(HTTP) requests from any outside IP address to the IP address of your web server at any time of
day. This rule is shown in Figure 4-5:
Figure 4-5: Rule example: A Local Public Web Server
Note: Some 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 the Acceptable Use Policy of your ISP.