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What is a public IP and how can you change that of your computer

22 mayo, 2021

In the same way that we cannot circulate on the roads without license plates, and that when we commit an offense, it is essential to identify ourselves and find us, when we surf the Internet we also have our own license plate: our IP address (acronym for ‘Internet Protocol’).

The parallelism, of course, is not perfect: the Internet is a world in which not only cars (Internet users) use this ‘license plate’, but also also each of the points between which these cars move uses a; Every time we access a website by typing in a URL, the browser simply translates that text into IP address format to know how to get to that site.

This IP is a number that identifies a specific device on a network and that allows us to communicate with it. In the event that said device is connected to the Internet through a home network, it will be assigned a different ‘license plate’ for each of the networks to which it connects:

  • The private IP: This IP is fixed, and is used, for example, to connect the device to a WiFi router. We can find out this number by opening the terminal window and typing ‘ipconfig‘if we work with Windows e’ifconfig‘if we do it with Linux: our private IP will be shown (both in IPv4 and IPv6 format) on the screen.
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An alternative to using ‘ipconfig’ is to access ‘Change adapter options’ and click on the ‘Details’ button of our Internet connection.

  • The public IP: It identifies our device on the Internet, so it is our supplier who assigns it to us, which in most cases will entail a periodic change of it (normally, every time we restart the router). how to understand this IP address (and all others)

How to change our public IP

Public IPs that change every so often are called ‘dynamic’, as opposed to the ‘fixed’ ones; If you don’t know which one you use, it is most likely the first one, since the fixed ones usually entail an extra payment. Dynamic public IPs are the easiest to change: as we have said, they usually vary each time you restart the router.

So check your IP with some of the many web tools that allow us to verify our public address for free, power cycle the router and recheck the IP when the connection is re-established: most likely it has changed.

Having a fixed (and unique) public IP is necessary if we want to set up, for example, a home web server with Internet access.

If this is not the case, and we know that we are not paying for a fixed IP, we can meet at a third case: that our provider is connecting us through a CG-NAT, a system that allows us to assign the same public IP to several different users.

This system can lead to problems when these users connect simultaneously to the same server (one of them could end up being expelled), or one of them is identified downloading illegal material (which can even lead to the arrest of the wrong person).

In the latter cases, it may be useful to resort to a VPN or a proxy: although this class of services they will not change our public IP, they will allow us to mask it for the websites we visit, which will only see the IP of the intermediary.