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After winning the first leg 2-1 in Addis Ababa last month, Victor Moses' 20th-minute penalty and substitute Victor Obinna's late free-kick secured Stephen Keshi's side their place at the finals for a fifth time in six attempts.
The hosts were strong favourites coming into the game, with the added benefit of two away goals from the first leg, and when Aynalem Hailu was deemed to have handled the ball inside the area, Moses dispatched the penalty leaving the visitors needing two goals just to force extra time.
In truth, Sewnet Bishaw's side created little, and when Obinna thumped home a 25-yard free-kick with eight minutes remaining it sealed a comfortable passage for Nigeria.
The hosts made two changes from the first leg with Brown Ideye and Kenneth Omeruo returning to the starting XI, while coach Bishaw made four alterations for Ethiopia, with first-leg goalscorer Behailu Assefa among those to miss out.
Nigeria's Emmanuel Emenike, who netted a double in the first leg, was the first to threaten, the striker seeing his close-range volley acrobatically parried away by Sisay Bancha in the sixth minute.
But it was a controversial incident that saw the home side take the lead 14 minutes later when defender Hailu was harshly adjudged to have handled the ball in the area.
The defender attempted to block a cross from the left, with the ball striking his thigh and bouncing up onto his right arm.
The referee, Bakary Gassama from Gambia, pointed to the spot despite strong protests from the visiting players, before Moses stepped up to send Bancha the wrong way from 12 yards.
Ideye twice wasted opportunities to extend Nigeria's lead before the break, heading narrowly wide from Ogenyi Onazi's right-wing cross on the half-hour mark before blazing over after Bancha had parried Onazi's effort two minutes before the interval.
In a largely uneventful second half, Bancha rushed from his line to deny Emenike on the hour, before Obinna – on as a 79th-minute replacement for Moses – sent a vicious dipping free-kick beyond Bancha.
The goalkeeper really should have done better, wafting an arm at the ball as it flew past him, but it was of no concern to Nigeria, sparking scenes of celebration at the final whistle.