Sometimes you need to run netca manually to configure Listener for your database. In Oracle 11g i found this message as a warning when selecting Database Control Configuration.
So planned to document this and of course this is one of the part of Oracle 11g Installation.
1. Open a terminal as a Oracle user and run netca.
Select -> Listener Configuration
2. Select Add, as we are going to create a LISTENER for a new setup. If we have any existing listener running on the Server, remain options will be highlight like "delete" "re-configure" etc.