Are you able to ping the computers from outside the game?
Also, you mention IP addresses settings, that isn't needed for a LAN game in Vavoom, you should start the game from the in-game multiplayer menu, once you have set it up, the other computers sh0ould use the join option from multiplayer menu and they should see the game listed by the host's computer name, not IP address. Let me know if you have any other problems with this and I'll try to help.