General
1. On both Wii U Consoles, go to System Settings > Internet > Connect to the Internet.
2. Press Y and select Wired Connection. Connect the LAN Adapter to the Wii U Consoles and press OK.
3. A communication test will begin and fail. Press OK to see the error results.
4. Press X to load up the Internet Connection Setup and go into the details of the connection.
5. Tab right and select IP Address. Select Do not auto-obtain and enter the following values.
Console #1
| IP | 192.168.000.001 |
| Subnet Mask | 255.255.255.000 |
| Gateway | 192.168.000.050 |
Console #2
| IP | 192.168.000.002 |
| Subnet Mask | 255.255.255.000 |
| Gateway | 192.168.000.050 |
6. The Wii U will ask you to set up DNS servers. Select Do not auto-obtain and enter the following value.
| Primary DNS | 001.000.000.000 |
7. Press B and save the settings. Do not run a connection test.
8. Load up the game and activate LAN Battle (See below).
LAN Battle Mode
To start up LAN Battle mode: Hold down [L Button] + [R Button] + [Down on the +Control Pad] then press [Start].
Reference
http://www.serebii.net/pokken/lanbattle.shtml
http://www.pokkentournament.com/en-us/article/?id=pokken-tournament-lan-mode