It was also a true test of character for Ian Costello's side and they showed they had that quality in abundance coming from behind three times to claim a final spot.
They led 9-6 at half time and were perhaps fortunate to be in that position because besides Leinster out-half Noel Reid missing with two penalties, the underdogs needed desperate scramble defence to close down the Leinster wide boys more than once. And when the home side sent their big boys racing for the line around the half hour mark only uncompromising defence stopped them short.
Credit too to Costello, Niall O'Donovan and their management crew. They resisted the urge to use the likes of Mick O'Driscoll in favour Ian Nagle and Brian Hayes and the Cork Con pair did not disappoint. Credit too for the way they used their bench, in particular bringing Denis Fogarty and Peter Borlase in at just the right time.
Credit too to the Munster set-piece that was a solid source of strength all night.
But perhaps the game was ultimately won and lost in the third quarter when tries from Luke McGrath and Dominic Ryan, both converted by Reid, saw Leinster turn a three point deficit into an eleven point lead. Ryan's try originated by a great break and run by number Leo Auv'a. At that stage Munster, facing into a stiffening wind, and down to 14 after Paddy Butler had been yellow carded, looked in serious bother.
However instead of bowing their heads, they bent their backs and produced two sparkling tries courtesy of Barry O'Mahony and Luke O'Dea to take a three point lead. O'Mahony's came when he blocked down an attempted Reid clearance and O'Dea's was a real gem. Good hands - Sean Scanlon especially - in tight space on the right left him in space in the 55th minute and it was no contest when it became a one-on-one with David Kearney, O'Dea skipping around the full back to race in under the posts.
Two more Reid penalties had Leinster three in front again but Deasy tied it up with 16 minutes left on the clock.
Deasy had the chance to win it in added time his long range effort drifting narrowly wide to set up a ten minute a-side of extra time.
Again it was Munster whose character was tested when Reid kicked Leinster in front four minutes into the first half of extra time. Again the response was immediate and Deasy levelled before the crucial score.
It began when Fogarty made yardage he had no right to make into the Leinster 22. The support was excellent, at it had been all night and the alarm bells were jangling as Munster went left then right to eventually breach the Leinster defence to the right of the posts, the superb Dave Kilcoyne crashing over to leave Deasy with a tap over.
By now Munster were running riot, Leinster running on empty. The only decent toe-hold the home side got in Munster territory was at the start of the second period of extra time. But once Deasy's relieving penalty took play into the Leinster half, that's where it remained as Munster ably led by skipper Billy Holland who had lad teammates queuing up to assist, saw it out reverting to 'old school' rugby for a place in the final against either Cornish Pirates or Cross Keys.
Leinster: D Kearney; A Conway, B Macken, C O'Shea, F Carr; N Reid, L McGrath; J McGrath, A Dundon, M Moore; D Browne, M Flanagan; R Ruddock, D Ryan, L Auva'a. Replacements: C Marsh for O'Shea (ht); A Boyle for Marsh (43 mins); J O'Connell for Moore (69); J Murphy for Browne (75); T Sexton for Dundon (77 mins): M Healy for Kearney (90 mins).
Munster: S Scanlon; L O'Dea, D Barnes, JJ Hanrahan, I Dineen; S Deasy, D Williams; D Kilcoyne, S Henry, J Ryan; B Hayes, I Nagle; B Holland (capt), B O'Mahony, P Butler. Replacements: D Fogarty for Henry (50 mins), P Borlase for J Ryan (50), C Sheridan for Williams (69); B O'Hara for O'Mahony (71), D Cusack for Hanrahan (76), P Donnellan for Holland (90-92 mins). Sin Bin: P Butler (Munster) 44 mins
Referee: I Davies (Wales)