Fortinet MR1 - Manual (Page 529)

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Delete Stub Area - Delete the stub area designation. The area will be returned to normal state.
Create NSSA - Configure the area ads a NSSA
Delete NSSA - Delete the DSSA. The area will e returned to normal state.
Submit - Send the updated configuration to the switch. Configuration changes take effect immediately.
These changes will not be retained across a power cycle unless a save is performed.