Leinster finished the league season top of the PRO12 standings, following an enthralling day of action that also saw Connacht book a home playoff semifinal, and Ulster secure their top four place.
Glasgow Warriors travelled to Galway to face Connacht top of the table but finished in third, following a 14-7 defeat.
The visitors had battled back from conceding the game's first try, scored by Bundee Aki, as Gordon Reid's score helped level things up.
However, Glasgow prop Sila Puafisi saw red after using his head to clear out from a ruck 10 minutes after half-time, before Tiernan O'Halloran notched the game-clinching try.
The two teams will meet again in the playoff semifinals after Leinster sealed top spot with a convincing 50-19 win over Treviso in Dublin that meant they edged out Connacht thanks to having won more games.
Jonathan Sexton scored the first try of the contest, but put a slight dampener on the result as he was replaced in the second half as a precaution.
Richardt Strauss (2), Jack McGrath, Isa Nacewa, Michael Kearney, Noel Reid and Garry Ringrose also scored tries in the rout. Sexton converted Strauss' second try, while Nacewa contributed eight points with the boot.
Marco Lazzaroni, Matteo Muccignat and Enrico Bacchin crossed the whitewash for the visitors, while Jayden Hayward added two conversions.
Elsewhere, Ulster set up a semifinal against Leinster with a convincing 46-26 win over Ospreys in Swansea.
Dan Biggar struck first for the hosts as he trotted over from close range, but Ulster hit back almost immediately through Paddy Jackson before Rory Best put them in front.
In all the visitors scored six tries, with Andrew Trimble, Chris Henry, Stuart Olding and Franco van der Merwe touching down to set up victory.
The Ospreys notched four tries in all with Josh Matevesi and Tom Grabham (2) also crossing.
Defeat ended the Ospreys' faint hopes of making the European Champions Cup, with Munster and Zebre winning to book their places.
Munster ran in five tries during their 31-15 defeat of the Scarlets, who in turn missed out on the playoffs.
Zebre secured arguably the result of the weekend, however, as they scored five tries to beat the Newport Gwent Dragons 47-22 and pip Treviso to Champions Cup qualification.
Oliviero Fabiani, Kayle van Zyl, Leonardo Sarto, Bruno Postiglioni and Kelly Haimona all touched down, while Carlo Canna struck 22 points with his boot.
In the day's other game, Cardiff Blues came from behind to beat Edinburgh 22-17 at Murrayfield and leapfrog their hosts, and the Ospreys, in the final table.