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How to open ports on a router or modem (DMZ, UPnP, public IP)

How to open ports on a router or modem (DMZ, UPnP, public IP)

Opening, forwarding or «mapping» ports, port mapping or shipping port in English, it is a procedure that allows you to access a computer in your network (let’s call it a target computer) from the Internet through a certain «channel» or port, for various purposes: remote control, viewing surveillance cameras ( 2) or be able to play online with other players (for example, when I can’t find you in games).

The barrier that exists and «prevents» access to computers on your network is your router. Therefore, port forwarding is a configuration that is done there. Since there are countless models, I will try to make a tutorial as general as possible based on my router, Huawei HG8546M, so you have an idea of ​​the procedure. Then you can go to, where you will definitely find the exact procedure for your router or modem model.

Router access data

The first thing you will need is the router access data, IP address, username and password. If you or your ISP have not changed them, you will probably receive the factory settings, which are usually on the label attached to the back of the device. In my case, those data are, root, adminHW.

Now, in the web browser of any device connected to the wired or wireless router, you need to enter the IP address of your router in the address bar. A page will appear, where you must enter your username and password and click on «Login».

The default IP of the router is generally not changed, so when you enter it in the browser you should see a login screen similar to the illustration. However, the default username and password may be incorrect. In this case, it is very likely that your ISP has changed this information. You should contact them to find out.

Fixed IP

Because port forwarding involves creating a «connection tunnel» from the Internet to the target computer on your network, that computer must have a fixed identifier: specifically a fixed IP address. Because routers are usually configured to assign random IPs to computers on the network (DHCP), you must first assign a fixed IP to that computer before mapping the ports.

Likewise, this configuration varies from one router model to another. In my case, the fixed IP option is under the «LAN» tab, DHCP Static IP Configuration. As shown in the illustration above, just click «New» to add a new configuration. You will need to enter the IP address you want to assign to the target computer, which will be similar to that of the router, except for the last digit. For example, in my case, the IP of my router is The IP address of my target machine can be If there is already another computer on the network with this IP, I can change 2 to any other number that is between 3 and 255.

In addition to the IP, you will also need to enter the MAC address of the target computer. If it’s an Android device, finding its MAC is easy. If it is a Windows PC, press the Windows + R keys. In the window that appears, type cmd and press Enter. In the command line, enter ipconfig / all. Your MAC will be on the line that says «Physical Address». If you have multiple «network adapters» (for example, if there are virtual machines installed), you should look at the adapter that says «Ethernet» or «Wireless.»

Opening the port

In the router configuration screen you will need to look for the port forwarding option. The most common name for this setting is usually Port Mapping or Port Forwarding. In my case it’s called Configuring port mapping, which can be found under «Rules ahead«.

On this screen, tap «New» to add a port forwarding. You will need to fill in several fields starting with Internal host, which should be the fixed IP address that you should have previously assigned to the target computer. On Protocol You must choose TCP, UDP or both and enter the port number or range of ports (you must enter the same for both the «internal» field and the «external» field). These values ​​will already depend on what the creator of the program or game that requires you to open the ports tells you. The rest of the data should be left as is, either empty or default.

The alternative method

In the router setup screen, you need to find and enable the UPNP option. In the case of my router, the option is called UPnP configuration, under the tab Network application.

Then go to Windows Explorer (you can open any folder), in the left navigation panel click on the «Network» tab. Your router should appear. Right click on it, Properties, Settings. Click «Add» and you’ll be able to add a port forwarding similar to the previous one. Click «OK» in all windows to save the change.

Some users have claimed that, through this method, they have successfully redirected the ports. However, in my case I saw that this configuration is temporary and disappears after restarting the router.


dmz router asus

The Delimited Zone or the Demilitarized Zone is an easier alternative to opening ports, which gives us the same result. It involves exposing a computer to the Internet so that it has a free connection through any port. After you add a device to the DMZ section of the router, it’s like it has all the ports open. It’s an easy way to find out if your connection issues are really due to closed ports or if you don’t know exactly which ports to open in a game.

Once you’ve set up a fixed IP on your Play Station, console, or PC, all you have to do is add that IP to your router’s DMZ, an option that’s usually in the WAN or «Port Forwarding» section. It’s that simple.

How to check if a port is open

there is online pages where I tell you to just enter the port number to find out if it is open or not. However, this is not enough. For the test to be successful, the target computer must «listen» to the requests from that port. If not, you will definitely see that the port is locked, despite opening it in the router.

An easy way to force a Windows PC to listen on a certain port is the portable and easy program Port Listener, from the developer RJL software. Run it, enter the port you want the program to listen to and press «Start». A Windows Firewall window is likely to appear, which you must «accept» to give the program permission to connect to the outside world.

Just after listening to Port Listener, enter any of the online pages to test open ports (I usually use for TCP and or for UDP ports), enter the port you are testing and click «Verify». You should see something similar to the illustration above: “Port 1234 is open on ″

My port is still closed

Before explaining the causes of this, you must first be completely sure that you have forwarded the port or ports on the router correctly. This tutorial may not be enough for this, as it is quite general, so you should review a correct tutorial on how to do it on your particular router model.


Some devices, such as Windows PCs, incorporate their own barrier or firewall that is responsible for preventing unauthorized Internet connections. Normally, the programs and games that you install should configure authorization rules in the Firewall during the installation process so that they do not prevent the received connections from working properly. However, if this is not the case or you are not sure, you can temporarily disable the Firewall and test if you have a successful connection through the open port. If so, you can manually create the required access rule in the Firewall so that you don’t completely disable it.

NAT double

What is Double NAT: Source: Ubisoft

The most likely reason that the ports you opened on the router appear to be closed, despite the fact that you tested them correctly as indicated above, is that you are under a Double NAT Internet service. This simply means that you are not directly connected to the Internet, but there is a second router in front («Second Router» in the illustration). In other words, even if you have opened ports on the router, this second router will work as an additional «wall», which is why I can’t see you from the Internet through the port you opened.

To find out if you have a Double NAT Internet service, you need to go to your router’s configuration and look for a similar option to «WAN Information». Click the Internet connection that appears (if applicable) and verify that the IP address in the «IP Address» field matches the IP address that your online pages show you. If the IP not it’s the same, so you have a dual NAT connection. If it is the same, then fortunately you have a simple NAT or a public IP, which I will mention later.

The solution to Double NAT would be to perform a procedure similar to the ones indicated, but this time taking into account the two routers. That is, in the second router, the port forwarding should indicate the IP address of the router. However, the second router is definitely under the control of your ISP or ISP, which is why you will need to arrange with their technical service to perform this procedure.

Public IP

The other solution to NAT duplication is to request a public IP from your ISP. This change converts your double NAT to single NAT or NAT. In other words, the second router I mentioned «disappears» so that your router connects directly to the Internet and there are no barriers between them that prevent you from «seeing» or «listening» through the forwarded ports. .

The disadvantage of public IP is that it usually has an additional monthly cost compared to what you already pay for the internet service. For example, in Ecuador, some Internet service providers charge $ 5 and others $ 10. This is a relatively good price compared to other ISPs that assign you a public IP only if you buy a corporate plan, which usually costs twice or three times as much as an internal plan.

reference: Wikipedia, Ubisoft, Netgear

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