Ulster looked to take the lead after just two minutes, but Bruce Houston’s penalty attempt rebounded back out off the post.
It was Leinster who opened the score in the 12 the minute when outside centre Gavin Mullin dived underneath the posts folowing a series of 5m scrums, with Harry Byrne adding the conversion.
Mullin crossed again just two minutes later with a well taken individual effort, with Byrne converting again.
In the second quarter, Leinster took charge and tries from winger Rob Russell and Rowan Osborne secured the bonus point by the 23rd minute.
On the half-hour mark Leinster crossed for their fifth try, with hooker Dan Sheehan profiting from the lineout maul.
Sheehan then got over for his second try, with Byrne slotting the conversion to make it 38-0 at the interval.
Ulster made three changes at the break, but it was Leinster who stormed out of the blocks with prop Tom Clarkson scoring from close range three minutes after the restart.
Ulster continued to apply pressure to the home defence and eventually got their breakthrough on 49 minutes, with captain Marcus Rea finishing off a hard-earned try. Houston added the conversion to make it 45-7.
Mullin pounced for his hat-trick before Ulster back row David McCann notched a maul try just shy of the hour mark.
Five minutes later, with Leinster temporarily reduced to 14 men, the Ulster set piece paved the way for another McCann try.
The young Ulster men persisted until the end and were rewarded with a bonus point try from Tommy O’Hagan in the 66th minute.
However, it was Leinster who deservedly had the final say when Patrick Patterson nipped over at the death to round off the win.
Ulster A team:
(15-9): Conor Rankin; Ethan McIlroy, Ross Adair, Hayden Hyde, Graham Curtis; Bruce Houston, Nathan Doak;
(1-8): Andy Warwick, Adam McBurney, Peter Cooper, Jack Regan, David O’Connor, Azur Allison, Marcus Rea (Capt), David McCann.
Replacements: Tom Stewart, Tommy O’Hagan, Paul Mullen, Matthew Dalton, Aaron Hall, Jonny Stewart, Ben Power, Luke Pollock.