It was tit-for-tat as Leinster looked for fast ball into space and Munster countered through a powerful scrum and swift breakdown work.
Leinster centre Tom Daly struck four penalties to two from Munster scrum-half Brian Haugh, though the home side were reduced to 13 near the end of the half as ref Stuart Gaffikin went card crazy, binning a third Leinster player as Haugh narrowed the gap to 12-9.
It was soon level when Daly was slow away from a ruck and Haugh made him pay from left of the posts. Then, Shanahan intervened on a weaving run to score. Daly’s conversion made it 19-12. But, they needed Farrell’s charge down for the insurance, converted by Liam Burke.
Leinster scorers: (D Shanahan, T Farrell try each; T Daly 4 pens, con; L Burke con).
Munster scorers: (B Haugh 4 pens).
LEINSTER: J Fitzpatrick; M McFarland, T Farrell, T Daly, E Quinn; B Holland, D Shanahan; E Byrne (c), B Byrne, D O’Byrne, J Sexton, G Thornbury, D Leavy, J van der Flier, P Timmins.
Replacements: J Lawless for O’Byrne 30; K Murphy for Lawless ht; D Lawler for Sexton 51; R O’Loughlin for Quinn 68; L Burke for Shanahan 72; C Kilcoyne for B Byrne 74; J Glynn for Holland 76; C Owende for Thornbury 78.
MUNSTER: D Sweetnam; R Jermyn, H McNulty, R Scannell, A Enright; T Kiersey, B Haugh; N Horan, W Foley, B Scott, S McCarthy, J Madigan, J O’Donoghue, D Ryan, J Fitzgerald (c).
Replacements: D O’Connell for Madigan, J Kind for Ryan both 58; S O’Leary for Scannell, M Abbott for Foley both 68; C O’Donnell for Horan 69; B Nugent for Haugh 70; D Hartnett for Scott 73; J McInerney for Enright 77.
Referee: S Gaffikan, IRFU.
Result: Connacht U20 7 Ulster U20 9 Scorers for Connacht: Try: A O’Meara, Con: D Leader. Ulster: Pens: S Olding (2) Drops: S Olding.