Meanwhile, Lansdowne will be forced to save their Division One bacon next Saturday against promotion hopefuls UCC.
Andy Doyle's side coughed up a 20-6 half-time lead on Saturday as they let Trinity in for two converted tries from Hugh Hogan and Barry Kinsella in the closing quarter.
The 20-20 draw - incredibly Trinity's fifth stalemate in the students' first season in the top flight - left Lansdowne at the bottom and left fighting for survival.
County Carlow mustered a losing bonus point at Oak Park, despite being outscored by four tries to one by UCD. Richie Murphy kicked 17 points as the midlanders avoided the tricky play-off thanks to Lansdowne's capitulation.
Six-time winners Shannon ran in four tries - two from Ireland rugby league player Ian Dowling - as they creamed Cork Con 37-20 in a repeat of last year's final.
Mick Galwey's power-packed side have scored a mammoth 171 points in their last four outings but the former Ireland lock was still left crowing about the two late tries gifted to Con.
Cian Mahony and Brendan Cuttriss were both on target for Con, after first half tries from Shannon hooker James Blaney and Dowling - allied to 13 points from the boot of Tom Cregan - springboarded the home side to a 23-6 half-time lead.
Shannon will face fourth-place finishers Clontarf in the final four.
'Tarf lost out 6-0 to Belfast Harlequins, courtesy of two Keith Pyper penalties. 'Quins, who face a semi-final trip to Garryowen's fortress Dooradoyle, will need to step up a gear according to newly-appointed coach Andy Ward.
"We were guilty of playing too much rugby across the pitch rather than in their half," said Ward.
"On another day with the set pieces working very well we would have been able to exert far more pressure on them.
"But it did us no harm to get a hard game for a change and it gave us plenty to ponder on before Garryowen."
Their play-off opponents ran out 26-20 winners over Blackrock thanks to a 21-point show from scrum-half Gerry Hurley.
Elsewhere in the top flight, Gillian Carruthers was on target twice as Dungannon scored nineteen unanswered points at a sun-splashed Crowley Park to outdo Galwegians 19-12. Namibian flyer Dirkie Strydom also bagged a hat-trick of tries as Ballymena ran eight past a poor Buccaneers side at Eaton Park.
The Pirates lost out 55-5 as Ireland Under-21 back row Trevor Richardson scored their only points in the first half.
2004/05 Season Ups And Downs:
Division One:Semi-finals: Saturday, April 30: Shannon v Clontarf (kick-off 2.00pm), Garryowen v Belfast Harlequins (kick-off 1.15pm, live RTE)Div One Relegation-Promotion Play-off: Saturday, April 23: Lansdowne v UCC, (kick-off 2.30pm)
Division Two:Promoted: UL Bohemians, St Mary's CollegeSemi-finals: Sunday, May 1: UL Bohs v Dolphin; Saturday, April 30: St Mary's v UCC (both kick-offs 2.30pm)Div One Relegation-Promotion Play-off: Saturday, April 23: Lansdowne v UCCDiv Two Relegation-Promotion Play-off: Saturday, April 23: Barnhall v Clonakilty (kick-off 2.30pm)
Division Three:Promoted: GreystonesSemi-finals: Saturday, April 30: Greystones v Suttonians, Clonakilty v Instonians (both kick-offs 2.30pm)Div Two Relegation-Promotion Play-off: Saturday, April 23: Barnhall v Clonakilty
AIB LEAGUE: Saturday, April 16 Results:
Ballymena 55 Buccaneers 5, Eaton ParkBelfast Harlequins 6 Clontarf 0, Deramore ParkCounty Carlow 22 UCD 29, Oak ParkGalwegians 12 Dungannon 19, Crowley ParkGarryowen 26 Blackrock College 20, DooradoyleLansdowne 20 Dublin University 20, Lansdowne RoadShannon 37 Cork Constitution 20, Thomond Park
Ballynahinch 5 UL Bohemians 22, Ballymacarn ParkDe La Salle Palmerston 24 Bective Rangers 18, KilternanHighfield 24 Malone 26, Woodleigh ParkOld Crescent 26 Midleton 31, RosbrienSt Mary's College 33 Barnhall 19, Templeville RoadUCC 47 Thomond 18, The MardykeWaterpark 18 Old Belvedere 13, BallinakillYoung Munster 48 Terenure College 29, Tom Clifford Park
Ards 52 Sunday's Well 19, Hamilton ParkClonakilty 17 Corinthians 15, Shannonvale CrossOld Wesley 33 Banbridge 12, DonnybrookPortadown 0 Instonians 41, Chambers ParkQueen's University 66 Ballina 0, Dub LaneSkerries 26 Connemara 19, HolmpatrickSuttonians 13 Greystones 18, John J MacDowell ParkWanderers 22 Bruff 35, Merrion Road
Round Robin Qualifiers:
Monivea 27 Nenagh Ormond 40, MoniveaNaas 14 Rainey OB 13, Forenaughts