This is a little "how to" to connect two PS4's to play LAN supported games without an internet connection. Possibly more with the use of a router. Some of you may have figured this out already. I discovered this little trick while trying to LAN Party Diablo3 at a buddy's house, who refuses to get internet service.

The only things you need are:
A LAN (ethernet) Cable
Two PS4's
Two copies of a LAN supported game. (I've only tested Diablo3, but others should work)
It's important to ensure that both systems are on the same firmware version and have the same software updates for the game you want to play

You are going to connect both systems directly together with the LAN cable. I believe you could connect more systems with the use of a router.

On the first system
Navigate to Settings -> Network -> Set up Internet Connection -> Use a LAN Cable -> Custom

Now you want to setup a "manual" connection with the following settings
IP Address: 192.168.1.xxx (xxx is any number between 2 and 254)
Subnet Mask: 255.255.255.0
Default Gateway: 192.168.1.1
Primary DNS: 192.168.1.1
Secondary DNS: 0.0.0.0 (should be zeroed out by default)

You can go ahead and test the connection once you're finished. It will fail, but that's ok. Follow the same steps with the second PS4, but be sure that the last set of numbers in the IP Address is different from the one you chose for the first console.

Now you should be able to start a LAN supported multiplayer game with both consoles. You may need to select this type of connection in the game itself.

That's it. Have fun.