There is no encapsulation type configured.
There is a mismatch in encapsulation types.
The interface is not receiving any keepalives.
The interface has been configured with the shutdown command.
The interface needs to be configured as a DTE device.
The wrong type of cable is connected to the interface.
Interface can be enabled or disabled with shutdown/no shutdown command. If you interface is
down, it will display administratively down status. You can bring up an interface having
administratively down interface using no shutdown command.