My brother and I wanted to play together in one of my own worlds after we had acquired fiber. Before it was possible to open to LAN and Play together without any problems, but after we got fiber it stopped working. 

 When I open to LAN, the world should show up on multiplayer and if it does not, you can go to direct connection and write their IPv4 address and then write the LAN address, when you are connected to the same internet.

 But what happens is that the world does not appear on multiplayer or can be directly connected.

1. Connect to a single player world and open to LAN
2. The other person goes into multiplayer
3. The world does not show up and it is not possible to directly connect, with IPv4 address