When a computer program requests an open to connect to the Internet, you have to forward it to your computer using your router's configuration page. Router setup varies from brand to brand, and even from model to model, but port forwarding works similarly on many different types of routers.
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To reach your router's configuration page, you need to know its IP address. You'll also need to know your computer's local IP address to forward ports. If you don't know these numbers already, find them using ipconfig. (press Windows-R and run cmd), type ipconfig and press Enter. Read the line labeled "IPv4 Address" for your computer's IP address, and the "Default Gateway" line for your router's IP. Ipconfig outputs a lot of data, so if you don't see these lines, scroll up.
IP addresses in hand, log in to your router by typing the number from the Default Gateway line into your Web browser's address bar. Enter the router's administrative user name and password when prompted.
Click Applications & Gaming on the menu bar.
Open the Port Range Forward tab, if it isn't already open. On the first empty line, fill in the range of ports you want forwarded with the Start and End boxes. Choose the protocol — pick Both if you aren't sure — and then enter the last section of your computer's IP in the IP Address field. Check Enable and click Save Settings. The Application box is an optional label for your reference.
DD-WRT (Including Buffalo Routers)
Click NAT/QoS on the main menu. Unlike most routers, DD-WRT only prompts you to log in after you click an option on the menu, so log in to continue.
Click Add to create a new blank line on the Port Forwarding tab. Enter the same port number you want to forward in both the Port From and Port To boxes. Pick the protocol, enter your computer's full IP address and check Enable. Add a label in the Application box for your own reference, and then click Apply Settings to finish.
Click Forwarding to open the Virtual Servers page, which is TP-LINK's term for port forwarding. Click Add New to start a new forward.
Enter the port to forward in the Service Port field, or enter a range of ports using a hyphen. Leave the Internal Port field blank. Fill in your computer's full IP address and set the protocol. Click Save to finish.