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Making your Computer Accessible from the Public Internet

Make Your Router Forward Connections to the Computer

Below is a text transcription of the "Router Issues & Port Forwarding" video that is part of the Making your Computer Accessible from the Public Internet tutorial series for troubleshooting remote access to server-based applications.

Router and NAT configuration

Many homes and businesses today use a NAT router to manage multiple computers and devices on one public IP address. It's a convenient setup, but can cause trouble when using server–based applications.

To explain briefly where the complication arises, it has to do with the public IP address. NAT routers take the public IP address for themselves and assign local IP addresses for the computers and devices on the local network, so that they are all effectively sharing the same IP address. The system works fine until you want to give people on the outside Internet access to files, shows, or other information on your computer. When they try to reach the computer through the public IP address, they actually reach the router, and the router doesn't know how to forward the connection to the appropriate computer unless it has been told how to do so.

Telling the router which computer to forward a connection to is called port forwarding. Each server–based application has a port number it works through. Its port number is very useful in giving the router the information it needs to forward a connection.

To save the trouble of keeping track of ports and configuring routers, many NAT routers now have what is called Universal Plug and Play, or UPnP. When UPnP is enabled on the router, applications on the computer can manage the forwarding themselves. The program will tell the router which port it will be receiving requests on and the router will set up the necessary forwarding so that information from the outside Internet can be directed to the appropriate local computer. This allows the ports to be managed by server–based programs from the computers they belong to, making network management less of a hassle.

There are times though when UPnP either isn't available on the router, or isn't enabled for security purposes, and manual port forwarding becomes necessary.

First, you need to determine which port the application uses and with which connection type—this can be either TCP or UDP. You can usually find this information in the program settings, in the program's help documentation, or online. Certain types of programs will use a specific port that is reserved for that type of application such as HTTP for web traffic, on port 80, or SMTP for sending email, on port 25.

Next, you'll need to log in to your router and access the settings. This process is different for every router, so you will need to find your router's help documentation and read how to do this and how to forward ports. The steps that follow can help guide you and provide insight to what you'll encounter with your router, but keep in mind this is only a starting point.

Access the router's software

One way to access your router's settings is to enter the router's internal IP address into a browser. Find the default IP address in your router's help documentation, or try searching your router's model number online. There are online resources that list the default IPs of various routers, or you might find your router has decent documentation available online.

Enter a username and password

You'll need to enter your username and password to access the router's settings. If you've never changed these from the defaults, try entering admin as the username, and for password try admin, password, 1234, or leave it blank. If these options don't work, you'll have to look in your router's documentation for correct login details.

Locate the port forwarding configuration section

The location of the port forward configuration section varies widely from router to router. Sometimes it will be obvious how to find the port forwarding, other times it will be under a description you won't expect, or buried within other menus such as: Local network, Gaming and Applications, Firewall, Virtual Sever, Advanced Settings, Configuration, or NAT.

The port forwarding screen

The router configuration screen where ports can be forwarded will vary from router to router. In many routers, the screen will look like a table. Knowing what kind of information is collected here will help you when configuring your particular router for port forwarding, and most likely includes some of what follows. Keep in mind, however, that your router's configuration might not ask for all of the following information, or may refer to each piece of information different from the examples presented here. This is only meant to be a guide.

An applications box, comments box, or name box.

This helps you to remember what application you are forwarding the port for. This area is for your use only, and what you input here won't affect the port forwarding.

Index, ID number, or Rule number.

This number might be assigned according to the next number available in the list, or you may be asked to assign the number. The number should be unique. It is for your use only, and what you input here won't affect the port forwarding. Some routers may not even allow or assign ID numbers.

Protocol or Port Type.

This refers to the connection type your application uses to exchange information, and will be either TCP or UDP. You can find this information in your application's help documentation. Occasionally, an application will use both TCP and UDP. If the port forward configuration screen doesn't give you the option of selecting both for your application, you'll need to enter a port forwarding configuration for each protocol.

Global, Public, or External Port and Local, Private, or Internal Port

This is where you enter the application's port you'll be forwarding. You can find the port you need to forward in your application's help documentation; the number will range from 1–65535. In most cases, you'll enter the same port number into both these areas. Some routers might not even give you the option of specifying a public or private port, but if they do, public and private ports allow you to forward to one port on two different computers. If you need to do this, enter a new, unused port number into the public port, and the application's actual port into the private port for each computer.

Start and End Ports

Some applications require you to forward a range of ports. Enter the first number of the range as the Start port, and the last number of the range as the End port. If you only have one port number to forward and your port forward configuration requires start and end values, enter the same number for both ports.

Server IP or Host IP

This refers to your computer's IP address. Sometimes you can select the appropriate computer name from a dropdown list, but most likely you'll need to know the exact local IP address. If you're running on Windows, obtain your computer's IP address by pressing the Windows key and R simultaneously.

In the window that appears, type 'cmd.'. A command window will appear, type ipconfig. Look for the IP Address, and write it down.

State or Enable

Enabling or activating the state of the entry will allow your router to forward the port as you have configured. If it is disabled, or inactive, the port will not forward.

Hopefully, once you've configured your router to forward ports, your application will be visible to the outside Internet. If you find you are still having trouble with port forwarding, you can try an alternative such as using a program that will automate port forwarding for you. It's also possible that port forwarding is only one of your problems. Check your firewall configurations through your operating system, your router, and through any third party security software you might have installed on your computer. You'll also want to verify you have a static IP address. Many Internet service providers assign temporary public IP addresses, meaning it's possible your public IP address could be changing every time you reboot your computer. Watch our video tutorial on the importance of static IP addresses for more information if you think this might be your problem, as well as our tutorials on Firewalls and STUN for more possible solutions by visiting the address on your screen. Good Luck!

Server-based Software Topics

IP Addresses
Router Issues & Port Forwarding
Firewall Configuration
Glossary of Terms

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