Ultimately, Leinster had enough scoring power to see them through and while Munster dominated possession and territory late on they could not unlock a brilliantly organised home defence.
Leinster now face an away semi-final against Jersey Reds, who beat Doncaster Knights yesterday.
A happy Leinster coach Noel McNamara was relieved to emerge from the derby.
“It was a tough game, we knew it would be, but I was delighted with the way we stuck to our task, especially in those last minutes when Munster attacked us a lot. In a sense it was a typical derby with not too many chances, but thankfully we were able to take ours.”
Munster struck first from the boot of Bill Johnston with a simple penalty in front of the posts 20 metres out in six minutes, but Leinster won valuable territory from a penalty and Peadar Timmins eventually wriggled his way over on 12 minutes, with Ciaran Frawley added the extra points.
Johnston cut the gap to one immediately with a well-struck penalty from distance.
For long spells afterwards there was little between the sides on an afternoon that became increasingly cold and damp.
The best opportunity fell to Frawley after 33 minutes from the tee at a favourable range and distance but his attempt was caught by the wind and hit an upright.
Despite all the young talent on view, the quality of rugby was only moderate.
A kick and chase from Munster full-back Stephen Fitzgerald early in the second half did cause problems for the Leinster defence until the visitors turned the ball over as they surged forward in search of a try.
That period of territorial dominance was all too brief and Leinster hit back with a spell on top; this time Frawley made the most of another penalty opportunity and he kicked the goal to make it 10-6 midway through the second half.
The home side built on that lead with a brilliant try from full-back Jack Kelly after 63 minutes. For virtually the first time, the Munster midfield defence was breached when Gavin Mullin made a clean break. He made ground and found winger Tommy O’Brien who cut inside to send Kelly over for the try that Frawley converted.
Munster didn’t give up on retaining their title and dominated to the finish but lost a scoring opportunity when Ronan O’Mahony failed to hold a pass as he drove for the line.
Though disappointed to bow out, Munster head coach Peter Malone was pleased with aspects of the performance, though he rued missed chances.
“I can say I was happy with our set piece and with the amount of possession we got from the game but ultimately it probably came down to not taking our chances.
“We fell 11 points behind but with almost 20 minutes to go but we had plenty of territory and scoring opportunities after that. Had we managed to get a quick score it would certainly have been game on.
“Unfortunately, we couldn’t find that scoring pass and we did knock on three or four times which didn’t help; that was the most disappointing thing from my perspective.
“Certainly, you would have to give Leinster credit for the way they defended and their kicking game was excellent at times during the game. This was a tight game throughout and I suppose in such encounters it often comes down to taking opportunities.
“They had two real chances in the second half, they got into good attacking positions twice and they scored a try and a penalty. That made it difficult for us, but to our credit we gave it everything in those last minutes; it was just that we didn’t take the opportunities when they presented themselves.”
J Kelly; T O’Brien, G Mullin, C O’Brien, B Daly; C Frawley, C Rock; E Byrne, B Byrne (captain), V Abdaladze; M Kearney, I Nagle; O Dowling, P Timmins, J Murphy.
M Bent for Abdaladze (44), P Dooley for E Byrne (60), H O’Sullivan for Dowling (76), R Foley for Rock (78), H Byrne for Frawley (79).
S Fitzgerald; C Nash, D Johnston (C), A McHenry, R O’Mahony; B Johnston, J Stafford; J Loughman, K O’Byrne, B Scott; S O’Connor, D O’Shea; D O’Callaghan, C Oliver, J O’Sullivan.
M Sherry for O’Byrne (39), C Parker for Scott (45), Scott for Loughman (injured, 54), J Power for Fitzgerald (59), J Poland for Stafford (62), J Foley for O’Sullivan (68). A Tynan for O’Mahony (73). J Daly for O’Callaghan (78).
K Dickson (R.F.U)