Leinster booked a Pro14 final date with Munster on 27 March after a bonus-point victory over Conference A rivals Ulster in Belfast.
In a game packed with incident, Leinster came from 12-3 behind and having two overlapping yellow cards by scoring tries from Michael Bent, Josh Van Der Flier and Ed Byrne to give them a 24-12 half-time lead.
The bonus point came in the second half from a Rhys Ruddock try before Dan Sheehan crossing for Leinster's final and fifth try in the last minute.
Ross Byrne kicked all five conversions and added a penalty.
Ulster had replacement prop Andy Warwick red-carded and Stuart McCloskey shown yellow while Leinster had Devin Toner and Jimmy O'Brien sin-binned in the first half.
Leinster’s Ruddock was also sin-binned late in the second half as was Ulster’s Cormac Izuchukwu on a busy night for referee Frank Murphy.
Ulster scored first-half tries through Marcell Coetzee and Robert Baloucoune with Nick Timoney crossing late on.
Ross Byrne got Leinster off the mark with a fourth-minute penalty after the returning Coetzee was penalised at the breakdown.
Shortly afterwards, Toner was yellow-carded by referee Murphy for a high hit on Michael Lowry and Ulster struck shortly afterwards when, after two penalties to the corner, Coetzee smashed his way over near the posts.
John Cooney converted to put Ulster 7-3 up and with Toner off the field, Ulster made the advantage pay with a marvellous move ending up with Baloucoune driving over in the corner.
Though Cooney hit the post with the conversion attempt, Ulster were now 12-3 in the lead though Leinster were reduced to 13 men as centre O’Brien was also yellow-carded for head contact with Ian Madigan.
With Toner back on the field, Leinster’s pack upped their game and when Ulster began to concede penalties in their 22, the visitors tapped two penalties with Bent crashing over beside the posts which allowed Ross Byrne convert to make it 12-10.
The reigning Pro14 champions – now back to 15 again – kept up the pressure and after Luke McGrath was brought down short of the line by Cooney, McCloskey was sin-binned and, once again, Leinster tapped the penalty allowing Van der Flier to wriggle through.
Leinster now had the lead and Ross Byrne's conversion made it 17-12.
Then Ulster were reduced to 13 as Warwick was shown red after his elbow made contact with Ed Byrne and not long afterwards the home team lost the talismanic Coetzee to injury.
With McCloskey still seeing time out on his yellow card, Leinster scored their third try when Ed Byrne barrelled over from close range, Ross Byrne converting again to stretch their led to 24-12 which is how the half ended.
Baloucoune then weaved through for what looked like a wonder score only for it to be ruled out due to an apparent block by McCloskey on Ruddock.
A series of penalties against Ulster around the hour mark saw the visitors launch several tap-and-go penalties and despite some resolute Ulster defence, Ruddock eventually barged through under the posts for the key bonus point.
Ross Byrne’s conversion took Leinster to 31-12 ahead.
After camping on the Leinster line – which saw Ruddock sin-binned – Timoney eventually got over after 72 minutes which Lowry converted.
The gamed ended when Sheehan crossed after Izuchuckwu’s sin-binning.