PPP is a protocol for intranet/Internet communications, and was often used for dial-up. However DSL Internet uses it too. It can be useful where only Serial/COM1 ports are available and Windows 11 still supports connecting to it. Firstly, connect 2 devices using the cable. On the router/server run a PPP daemon / server, and use your serial port. Maybe Server 2025 can do it, I am not sure, I use Debian to do that. Once the other computer has PPP listening, go to Device Manager and click on your computer name. Click Action, then Add legacy hardware. Select it from a list, click Modems, and select it from list. Use "Communications cable between two computers". Select your COM port. Install it and it should be done. Now go into dial-up settings, click Set up a new connection, and use the workplace button. Click dial directly and click set up anyway. For phone number use 555-555-5555, use "user" and "pass" for username & password, and create it. Connect it, and you should be good to go. In my case, because I didn't want to mess with iptables, I had to configure a Web proxy.