my fc6 automatically connects internet when it starts... i want it to manually connect/disconnect to the internet... how can i do that???

Most Linux distros have taken great pains to get their systems to auto-detect Internet connections, as most users want to do this without the hassle of manually doing so.

You can go to System-->Administration-->Networking and highlight your ethernet connection. Choose the edit button and uncheck the option of starting the connection on boot. Then save the changes.

When you want to start the connection, go back to System-->Administration-->Networking and activate the connection.