I decided to write this article to help all those users who have subscribed to the fibre modem provided by the operator, encounter problems with steam and the games associated with it. Among the problems, we can mention, for example, the browser in the steam that allows us to see the list of server favorites, etc...Someone suggests on the internet the classic solution that is the one of the port mappings but is not sufficient, as the nat is undoubtedly moderate.
Having the telecom fiber, for convenience, I will insert in this example, the data for the connection telecom, which, however, vary from vendor to vendor. You can request them, however, by calling your internet service provider.
In short, steam - "closed":
1. Control panel\Network and Internetetwork Center and sharing.
2. Select "set up a new network connection".
3. In the window that opens, select "Internet Connection" and click "Next".
4. In the next window click on "Configure a new connection anyway".
5. In the next window, create a "new connection" and click "Next".
6. In the next window, select "Broadband (PPPoE)".
7. In the next window, in user name, type (without the quotation marks) "aliceadsl" and as password "aliceadsl". Select remember password, give a name for the connection, for example "Nat" and click on "Connect".
The pc will attempt the connection and after a short time you will see on the right the icon that will inform you that you are connected to the connection "Nat".
At this point, open Steam-View-Servers, and you should correctly see the server in your favorites list. This procedure will unlock the nat for all the games of course.
Remember the next time you reboot to reconnect by right-clicking on the icon in the bottom right because the connection is not permanent, and sometimes it might disconnect.
I hope I was helpful!
I put also a video that better explains the procedure.