When you select Forward on Busy/No Answer, your calls are redirected to the number entered in the Forward on Busy/No Answer field. The same number is used for calls forwarded when your extension is busy or not answered.
Forward on Busy/No Answer works in the following ways:
The first time you select Forward on No Answer, the option Forward Internal Calls is automatically selected. If Forward Internal Calls and Forward on No Answer are de-selected, the next time Forward On No Answer is selected, the option Forward Internal Calls is not automatically selected.
If you have set an absent message, the text is displayed to callers when the Forward on Busy/No Answer forwarding option is selected. If absent text is active at the destination extension it will not be displayed because your absent text takes priority.