Port Forwarding - NETGEAR CG814W Reference Manual

Reference Manual for the Model CG814W Wireless Cable Modem Gateway
• If the service you would like to block is not in the predefined list, you can add a custom
service. Enter the range of ports you would like to block and select whether the ports are
TCP, UDP or Both. Click Add.
• To delete an existing rule, select its button on the left side of the table and click Delete.

Port Forwarding

Because the CG814W Gateway 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.
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.
Considerations for Port Forwarding
• If the IP address of the local server PC is assigned by DHCP, it may change when the PC is
rebooted. To avoid this, you can assign a static IP address to your server outside the range that
is assigned by DHCP, but in the same subnet as the rest of your LAN. By default, the IP
addresses in the range of 192.168.0.2 through 192.168.0.9 are reserved for this.
• Local PCs must access the local server using the PCs' local LAN address (192.168.0.XXX, by
default). Attempts by local PCs to access the server using the external WAN IP address will
fail.
Remember that allowing inbound services opens holes in your firewall. Only enable those ports
that are necessary for your network.
The following are two application examples of inbound rules.
4-6 Protecting Your Network