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What is port forwarding and why would I want to do it?  

What is port forwarding and why would I want to do it?
You may have heard about port forwarding before at some point. The internet uses a protocol called TCP/IP in order to transfer information. TCP/IP uses a series of virtual ports; different ports are used by different functions and applications. Port forwarding is forwarding a port "in front" of your firewall; this essentially means you're unblocking the port. Although ports are necessary in transferring data, leaving all of your ports "open" or unprotected can be dangerous. People can use open ports to spread viruses, spyware, and even to potentially take control of your computer. By using a firewall you can protect ports by blocking their incoming traffic. However there are times when you must utilize some ports therefore removing them from your firewall is necessary.
How you forward ports changes depending on what kind of firewall you have. In this case we will demonstrate using the Windows XP firewall and a Linksys router. Port forward is something you will need to setup for certain applications. File Sharing applications that require constant access to a specific port is an example of this. Other applications that might require port forwarding include certain chat clients, games, and just about any application that shares data, or establishes a permanent connection over a port.
First let’s take a look at the windows XP firewall. Microsoft has included a basic firewall with windows and has increased its effectiveness greatly in Windows XP Service Pack 2. The firewall we are looking at is the improved windows firewall included in windows XP service pack 2. To Forward a port in the windows fire wall go to start>control panel>firewall and then click on the exceptions tab. Click add port; here you can specify the name of the exception and the ports you want to forward. If the exception has a check mark next to it the exception is active and the port is forward. If there is no check next to the exception then this is not currently active.

Next we'll cover how to forward ports in a router. We'll be using a Linksys router as the example (in the picture below) however the method is near the same in all routers. The first step is to log into your router. This is done by typing the LAN IP of the router into the address bar of your web browser. See the knowledge base article Router information for information on user name and passwords and LAN IPs for various brands of routers. After you have logged into the router you should see a heading labeled port forwarding, gaming and applications, or exceptions, navigate to this tab. Routers allow you to forward a group of ports to an IP address on your network. Meaning that the ports will be forwarded for the computer with the IP address you have specified. You may specify a single port by specifying the same port as the beginning and ending port or you may specify multiple ports by specifying a range. Routers will generally give you a choice between UDP and TCP protocols. Most of the time you will be using TCP, however selecting both is acceptable in almost all cases. You may then specify the IP address you want to forward this port to. Simply establish the port range, protocol and IP address and click the apply button and then port forward is then complete.


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