How to Check Open Router Ports: Configure Ports

What is the use of opening the ports of the router?

If you are going to configure a server for something on your local network, where it is necessary for them to access it from the Internet, you need to open ports. For example, for the following uses it is necessary to open ports:

• Set up an FTP server to remotely access your files.
• Set up a VPN server to access your local network securely.
• Set up an SSH server on your computer, to control it remotely.
• Set up a mail server or web server.
• If you are going to use Nextcloud’s private cloud to sync files or folders.
• If you are going to play online, it is necessary to do port forwarding in the games, because we ourselves act as a server.
• If you are going to download via eMule, it is necessary to open the ports so that other peers can connect to you.
• If you are going to download via BitTorrent, it is necessary to open one port or several so that other peers can connect with you so that you can download and upload faster.
• Any other use that requires a connection from the Internet to your internal local network (PC, server, console, etc.).

Finally, if you are going to use games on your console, it is recommended to open the DMZ to the consoles, because they usually use many different ports for each game that we are using.

All home routers use NAT to go out to the Internet with multiple devices simultaneously, using the same public IP address. When a computer on the LAN (internal network) tries to access the Internet, NAT is in charge of translating addresses and making use of TCP / UDP ports without having to do anything, it is completely automatic and transparent to the user.

However, if communication starts on the Internet (WAN, external network) to the LAN, it is necessary to open a port to correctly redirect the packets to their destination. As you may have noticed, LAN computers use private addressing that is not routable through the Internet. To make them accessible from the outside, we will have to “open a port” in NAT, so that all the packets that reach the public IP and a specific port are correctly redirected to their recipient.

Before we start explaining how to check open ports on your router, let’s start by explaining the IP classes we have on a home network. To perform a port scan to check the open ports on your router, you have to do it towards a specific type of IP, specifically the public IP that our operator provides us.

Differences between public IP and private IP

An IP could be defined as a logical and unique identifier for each of the computers connected to a network . In addition, an IP address in IPv4 networks is made up of four groups of numbers between 0 and 255 separated by dots, with a length of 32 bits. These addresses are represented in decimal notation separated by periods such as the address 192.168.1.1.

Regarding IPs, we could say that there are two classes:

1. Public IP .
2. Private IP .

The public IP is the identifier of our network facing the Internet, that is, the one that you have assigned in your home router in the Internet WAN interface. This public IP you cannot put what you want, in this case it is your service provider (operator or ISP) that assigns you one, either statically or dynamically (the latter is the most normal).

Also within the public IP we have two categories:

1. The static public IP , that means that it will never change and it will always be the same.
2. The dynamic public IP, that means that it can change when the router is turned off, or after a period of time that our provider decides.

Today the vast majority have a dynamic public IP. Static IP is usually used by companies to set up their servers, and in addition to paying for the Internet connection, they have to add a small cost for having that fixed IP. As for the private IP , it is the one that identifies each of the devices connected to our network. Therefore, we refer to each of the IP addresses that the router assigns to:

• Our PC.
• To the smartphone.
• To the tablet.
• The smart TV or Android TV device.
• Other devices like smart plugs, IP cameras and more.

In summary, we can say that the devices connected to the same router have different private IP addresses, but the same public IP. In this sense, it is the router that acts as a gateway to communicate with the outside.

How to know the public IP of the Internet connection

Visiting a website that will tell us the public IP

If we want to know what our public IP is, that is, the one that identifies us outside our own network, we can do it through a web easily and quickly. Simply by using a browser in Windows, Android or Linux you can easily find out. We are going to use the web whats-my-ip.net and clicking on the name of the web you will know your public IP address. This is the result that I have obtained from my Windows 10 laptop:

From here, we extract our public IP which is 95.127.152.X. In addition, we have the possibility of geolocating the place where that IP is located and also shows our Internet provider.

Going into the router settings

Another method to know what our public IP address is, is by entering the router directly through its default gateway, in the “Internet status” menu, we can see something like “WAN IP Address”, this IP will be the Public IP that the operator has provided us.

Check open ports on your router

Once we are clear about all the concepts, it is time to check the open ports on your router. To do this, we mainly have two options, the first one and the easiest, is to use a specific website to check that our ports are open. We recommend you access our port test to check it quickly and easily.

Once we have entered, we will simply have to put our public IP address, and put the port or ports that we want to check. This tool allows you to check port ranges and also comma separated ports.

On the other hand, we always have the possibility of Android network apps. One of them is Network Scanner that you can download from Google Play:

In the tools section we have the Port Scanner option. Remember that to do it correctly you have to do it connected via mobile data, and put the public IP that we have in our home, and then indicate the ports to check and click on “Start”.

Then a list will appear with the open ports it has detected.

If it turns out that all ports are closed, even if you have opened them, we recommend checking the following parameters.

Check the private IP configuration of the PC, console or server

To see why the opening of ports has not worked, the first thing we must do is see what private IP we have on a certain computer. If we want to know our private IP we will do it differently. For example, this would be the way to do it from Windows 10 for a laptop or PC:

1. Let’s start .
2. We put cmd and press enter.
3. In the command prompt window we write the command ipconfig and give enter.

These are the results I have gotten from my laptop:

In this case, the private IP assigned to it is 192.168.43.184 . The default gateway is the IP of the router or access point that gives us access to the internet. If we wanted to do it on Android, we would go to Settings , double click on the WiFi network to which we are connected and it would give us the following information.

Now we see that our private IP is 192.168.43.79. We can also deduce that the range of our local network is 192.168.43.X and that all the devices are going to be within that range, since we are using a / 24 or 255.255.255.0 subnet mask.

Put fixed private IP so it never changes

Whenever we receive a packet over the Internet, it is destined for our public IP address, and also for a destination port. Thanks to NAT, we will establish communication with our local network of the data that comes to us from the public IP. NAT comes from the English Network Address Translation and is integrated into all the home routers we have today when we use the IPv4 protocol.

Today’s home routers have two interfaces:

1. WAN that is going to provide us with a public IP address.
2. LAN that provides a range of private IP addresses.

If we want to establish contact within the LAN, use the address of the LAN itself, so as not to need to go to the WAN. However, if we want to establish a connection from outside the network and access from the Internet, we will not be able to use these LAN addresses, we need to go through the WAN interface, and to do this, we must go through the NAT of the router «opening the ports ».

Generally our private IPs are automatically assigned by DHCP , and these IPs can change. If you are going to open ports to a PC, server or console, you will have to use fixed private IP addressing, so that the private IP does not change by the DHCP server.

Static DHCP

The most recommended method to have a fixed private IP on our devices is to use the Static DHCP feature. The vast majority of routers allow you to assign a private IP address to a specific MAC address, so that the DHCP server always provides you with the same fixed private IP address and that it never changes. Depending on the router, this option is usually in the LAN / DHCP section, and we only have to put the MAC address of our network card, and the IP address that we want.

To get the MAC address of our card, just go to “Start” and put “cmd”, press enter and put the following command in the Windows terminal: ipconfig / all . This command will show us all the network interfaces, and also the MAC address where it indicates «Physical address».

Once the MAC address has been obtained, it is enough to indicate it in the “Static DHCP” of our router, in the case of ASUS routers, this is done in LAN / DHCP and in the section “IP address assigned manually according to the DHCP list” .

Put fixed private IP directly on PC, server or console

If we want to put a fixed private IP on a PC, server or console, we can also do it manually. In Windows 10, we go to Start , Settings , Network and Internet and Change adapter options . Then we double click on the adapter , properties and Internet protocol version 4 (TCP / IP v4) . We would get a screen like this:

In IP address we put the IP that we want, to later open the ports. You can find out the subnet mask in the image and the gateway with the ipconfig command that I explained before.

Open the ports on the router correctly

In our router, now we would have to put the fixed private IP address that we have previously configured, and the external (and internal) ports that we want to configure. Normally the external and internal ports are always the same, so just filling in the “external port” option is enough for port forwarding to be successful.

In the following example we have used an ASUS router, we will simply have to fill in:

• Service name: to give you a description.
• Protocol: TCP, UDP or TCP and UDP at the same time.
• External port: the port that we want to open facing the Internet WAN.
• Internal port: it is optional, if nothing is entered, it will be the same port that we have defined in «external port».
• Internal IP address: Fixed private IP address that we have previously configured.
• Source IP Address: If we want only one source IP to be able to access it remotely, most routers do not have this option.

With this we would already have the ports open to our PC. Our router will know where to send the packets and they will not be lost. Once the changes have been applied, you should run the open ports test again to check if they are already open correctly, if they are not, check the firewall of your PC, server or console, since it is possible that you have it closed. If the port test keeps saying that the ports are closed, put a comment and we will help you solve the problem.

An important aspect is that it is very likely that we have the UPnP protocol or also called Universal Plug and Play activated. It is a protocol that allows you to auto-configure the NAT address table to be able to receive files without having to open ports on our router. Programs that support this protocol will open ports automatically and dynamically, but our recommendation for security is that disable this protocol.

We hope that with this guide you can open ports on the router without problems, and check that they are indeed open well.