Categories: TechTutorials

Why is it important to scan the router ports? We tell you

The ports of our router they are an important part of everything that has to do with our own Internet connection and how certain programs interact with it. But first we must know what they are exactly, what they are for and how we can interact with them.

We must understand what we are talking about in order to explain how to scan them and how we can work with the ports of our router, something that can make a good difference in certain situations.

What are router ports?

We know that the router is the device in charge of sending our entire home the data from our Internet connection so that computers, smartphones and other devices with connection capacity can be integrated into said network.

We can be connected to the router by cable, but the most normal thing is that we do it through the WiFi connection. The moment you connect to a web page, for example, from our router and the device we are using, a continuous data exchange. In order to send this data the router uses a series of channels, which we call ports.

All the routers have a total of 65,536 ports, having three differentiated groups:

Those that go from or to 1023: those that are used for the operating system and for important protocols such as FTP or HHTP.
Those between 1024 and 49151: These are usually dedicated to programs or games that we have installed.
From 49152 to 65535: They are dedicated to those programs that need to register on a server, such as those dedicated to download programs.

Types of ports

There are two types, TCP (Transmission Control Protocol) Y UDP (User Datagram Protocol). Surely the first is the one that you have heard the most, since it is the one that is dedicated to handling end-to-end connections, being ideal for the IP protocol. UDP are those that are used mainly for voice or streaming services, since they are much faster than TCP. Another difference between them is that the TCP protocol header is 20 bytes, while the UCP is made up of 8 bytes.

Why is it important to scan them?

The main reason for scan the ports of our router it is to know which of them are open and which are closed. When we have an operator router and we scan, we realize that the vast majority of them are blocked to try to protect the user. It is true that we must be very attentive in this regard, since some can be used in a bad way and use them to enter our network, but it is also true that there are some that must be open for the proper functioning of many programs, games and even systems such as streaming.

How to scan

In order to scan the ports of our computer there is no better way than to use some third-party applications that are prepared for this purpose and that will show us all the information we need in this regard in a clear and concise way.

Scan with TCPing

This is a tool that runs through a console, very similar to Windows ping, but using the TCP protocol. It is able to show us in an extremely reliable way whether a port is open or closed.

To use TCPing, the first thing we have to do is download it from your official Web. Once we have downloaded it, we must follow these steps to be able to work with it:

We open the Command Prompt in Administrator, typing cmd in the taskbar for when it appears at the top of the window, right-click and choose Execute as an administrator.
We go to path where we have saved the program and we put the executable file (tcping.exe) to open the software and get it running.

We will see how the TCPing help menu comes out first directly on the screen, where we can see all the parameters that we have at our disposal. The ones that are not most interesting are:

-4: IPv4 protocol.
-6: IPv6 protocol.
-t: ping the TCPs until we cancel ourselves by hitting Control-C.
port: With this command we can scan the port we want. If we do not put any, it scans the 80 by default.
-n NUM: performs a specified number of pings to a host. Replace NUM by the number of times you want.
destination: IP or domain of the host that we want to scan.

Scan with Zenmap (Nmap Graph)

Nmap is a free and open source tool that allows us to scan all types

of ports, networks and hosts, both in Windows and Linux and also in macOS. It also works by commands like the previous example, but it is true that it has a version called Zenmap in which we can enjoy a graphical interface and thus it will be easier for us to handle.

Once we have it downloaded and installed, we only have to run it to start using it. It is very easy to put it to scan, since we only have to put our IP address in section Objective and start with the scan, choosing which type we want is the one we want to perform.

At the top of the program we have a few tabs that give us additional information, but the one that interests us is the one that says Ports / Servers where we will see all those that are open and filtered at this time. We must be clear that depending on the type of scan we have chosen, that is how they will appear more or less in this section.

Open ports

It may be that a application cannot connect to the internet correctly if we do not open a specific port, so there we have a powerful reason to make them stop being blocked.

But it is also true that ports should not be open forever, unless we work with them continuously, in which case they are fine as they are. But if you are going to open a port and it turns out that you will not use it again for days, it is best to close it the moment you stop working with it, since it could be a place where some type of attacker enters and later Let’s put our hands to our heads

How to open them

To open them we must be clear that each router has a different interface, so the menus will not be in the same place, but they should be more or less called in a similar way and as an orientation it could serve us. we are going to do it on a Jazztel router.

The first thing we have to do is type the address in the browser http://192.168.1.1 and press Enter. This is the address that almost all routers go in.
Then he will ask us user and password. In many cases it is admin for both cases or it may also be that the username is the operator’s name, while the password is admin. If we do not know, we must contact the company that provides us with the Internet.
Now the router menu opens and we must go to Advanced configuration and then to Network settings.
In the center we select NAT / PAP and then in application / service we choose which one we are going to use.
Now we choose the internal port, then the external port and then the protocol TCP or UDP and even both.
Now we simply give in Add and that port is already open.

How do we know which port to open?

The best way to know which port we can open and which one not, is to know the main TCP and UDP and what they are used for, unless a specific program or game asks us to leave a specific one open.