What is the purpose and reason for using management, AP-manager, virtual, and service-port interface?
My bad... I mean WLC
In band is telnet, ssh to the management ip. out of band is when the port has no real connection to your network. That is why the ip address of the service port is an ip address that is not part of your network nor should it be routable in your network. In case you loos connection to the management and you don't know the commands for the cli, you can connect to the service port and use the gui.