The away win meant there was no need for the calculators as Cavan qualified as best runners-up and will now take on Tyrone, with the winner meeting Derry in the final.
Fermanagh’s Paul Ward, Paul McGrath, James Connolly and sub Tomas Corrigan all chipped in with scores, while Donegal’s most effective moments came from Adrian Hanlon and Jamie Doherty.
Donegal manager Jim McGuinness handed out seven senior inter-county debuts ahead of next weekend’s NFL opener against Sligo.
DONEGAL: P Boyle; T McKinley, E Doherty, F McGlynn; L Keaney, D Curran, K Cassidy; O Doherty, C Classon; P McNelis, J Doherty (0-2), O MacNiallais; A Hanlon (0-3, 1f) , R McErlean, M Boyle (0-1). Subs: K Lacey (0-1) for M Boyle (21) B Dunnion for McKinley, R Bradley for O Doherty (36), P McGrath for McGlynn (55), N McGee for Classon (57).
FERMANAGH: F Murphy; P Sherry, B Owens, M Jones; P McCusker, B Mulrone, T McElroy; H Brady, J Melarkey; P McGrath (0-3, 1f), K Cosgrove, N Cassidy; C Leonard, P Ward (0-4, 1f), J Connolly (0-2). Subs: C Quigley for P Sherry (20), T Corrigan (0-2, 1f) for Leonard (42), C Flaherty (0-1) for Cosgrove (47).
Referee: Martin McErlean (Derry).