England virtually assured themselves a play-off to reach the 2009 European Championships with a patient victory.
Theo Walcott and James Milner unlocked the Republic defence
The hosts broke the Republic's spirited resistance on the hour mark when Stephen O'Halloran deflected James Milner's low cross into his own net.
Andy Keogh wasted three decent close-range chances for the visitors.
And as Ireland tired, the excellent Milner drilled in a low drive from 25 yards, while Theo Walcott sealed the win with a delightful clipped finish.
Stuart Pearce's side now need only a point from their final group game against Portugal to claim top spot and guarantee a play-off place.
England U-21 coach Stuart Pearce:
I think this win will be enough to take us into the play-offs, we feel this will get us there.
"I'm delighted with my team. It took us a while to break them down but we learned how to be patient.
"We never looked liked conceding and had a good cutting edge going forward."
England U21: Hart, Gardner, Wheater, Taylor, Mattock, Lennon, Noble (Surman 85), Muamba, Huddlestone (Jerome 79), Milner, Walcott (Johnson 85).
Subs Not Used: Lewis, Mancienne, Moore, O'Hara.
Booked: Wheater, Johnson.
Goals: O'Halloran 60 og, Milner 68, Walcott 78.
Rep of Ireland U21: Randolph, Nolan, O'Cearuill, O'Dea, O'Halloran, O'Toole, Garvan, Quinn (Morris 83), Stokes (O'Brien 87), Clarke (Rooney 65), Andrew Keogh.
Subs Not Used: Supple, Richard Keogh, Dennehy, McFaul.
Ref: Jouni Hyytia (Finland).