should point out, if you are using a computer that is behind the same router it will allways appear to be lan, as it is lan for you, that doesnt mean others wont see it in there server brouser list. other users will connect via your ip, you however will conect via the lan ip.
all i did for my lan server is open up the required ports
ports UDP 7777-7790 (tbh i think you only need 7777 to 7784 iirc but thats the full package i think)
port UDP 27900 (is the port that advertises the server so people can see it in the brouser)
and port TCP 8080 (but thats for webadmin which you might not care about)
and people could join fine, and i join via lan tab