No problem: Port forwarding

I cannot get a multiplayer game to work online. It is not being blocked by the firewall on the computer. The problem started when I installed a broadband modem router instead of the USB broadband modem.
Tamsin Potter

The problem here is that because the router sits between the computer and the internet, the games can no longer communicate properly. This is partly so several computers can connect to the internet using the router, but it also has a significant security advantage. It is possible to open a channel for the games to communicate with the internet.

First the computer with the game must be set up with a fixed network address (also called an
IP address). Most routers assign these automatically, but this can lead to the number changing, which will stop the game again.

This example uses a Belkin router but if you have a different brand, try this website – it lists port forwarding instructions for most routers. There are 255 addresses available for the network starting at 192.168.2.1, then 192.168.2.2 and so on up to 192.168.2.255. The router only uses the addresses up to 192.168.2.100, so any number above this is available.

It is crucial to keep a note of which computer is using which address; if two computers try to use the same address, the entire network will stop working. Other routers may use a different range of addresses so check with the manual if you are unsure. Before going any further you will also need to make a note of some other information that will be needed. Click on the Start button and select run.

Type ‘cmd’ without the quotes to start the Command Prompt. Type ‘ipconfig /all’ (again without the quotes) and write down the numbers for Default Gateway and DNS Servers. To change the IP address of the computer, left-click on the Start button and then on Control Panel. Click on Network and Internet Connections and then Network Connections. Right-click on the icon called Local Area Connection and select Properties.

Scroll down the list in the window, click on Internet Protocol (TCP/IP) and then on the Properties. Click on ‘Use the following IP address’ and enter 192.168.2.101 in the IP address box, 255.255.255.0 in the Subnet Mask box, and the Default Gateway and DNS information that you wrote down earlier. Finally click on OK. Start internet explorer and the enter network address of your router, in this case 192.168.2.1.

Click on the Login option at the top right of the web page. Enter the password if one has been set up and then click on submit. Just click on submit if there is no password. Click on the Virtual Servers option in the Firewall section. Click on the dropdown menu labelled Add, find the game you want to play and then click on the Add button.

Add the network address of the computer that will be playing the game in the Private IP address section. If you followed the instructions above it will be 192.168.2.101. Click on Apply Changes at the bottom of the window to save the settings. If the game is not listed you will need the port number(s) that will be used. Click the enable box in the next available line so that a tick appears and then enter a description in the next box.

Enter the port range in the next two boxes. If only one port is used, enter this number in both boxes. The manual should explain whether the type should be set to TCP or UDP. If in doubt, try TCP first. Enter the private IP address and then the port for the local computer. This should be the same as the inbound port. Click on Apply changes.

If this does not work, the other possibility is to place that one computer in the DMZ (demilitarised zone) This effectively places it outside the protection of the router so make sure that it has adequate anti-virus and firewall protection of its own. Click on the DMZ option in the Firewall section. Enter the IP of the computer and then click in the enable box so a tick appears. Click on Apply Changes.

When you have finished with the game or application, return to this page and remove the tick to bring the computer back under the protection of the router.

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