SHANNON 17 GARRYOWEN 17, Thomond Park Stadium
Scorers: Shannon: Try: Fiach O'Loughlin; Pens: Tadhg Bennett 4
Garryowen: Try: Lorcan Bourke; Pens: Conor Kilroy 4
Number 10 Tadhg Bennett ensured the stalemate in injury-time, after winger Lorcan Bourke's 78th-minute try had nudged Garryowen into a winning position.
Bennett and Garryowen full-back Conor Kilroy swapped place-kicks for a 6-6 interval score-line. Both sides opened up as the intensity increased in the second half.
Man-of-the-match Fiach O'Loughlin touched down for a 14-12 Shannon lead but Kilroy put Bourke over to set up a tense finish in which Bennett brilliantly held his nerve.
Meeting for the 22nd time in the AIB League and for the first time under floodlights, Shannon and Garryowen served up an after dark thriller in front of a bumper crowd numbering 4,000.
In truth, neither side deserved to lose but with the two Limerick giants struggling for early season form, down in 11th and 12th in the Division One table, tonight's draw means they have lost further ground on the league pace-setters.
The opening quarter was cagey and neither the hosts or Garryowen, who were hoping to end a three-match losing streak in the league, could find their rhythm.
Scoring chances were few and far between, but Kilroy and Munster's Kieran Lewis and Ciaran O'Boyle looked dangerous when on the ball for Garryowen.
Shannon had their scrum half and captain Fiach O'Loughlin back in the team after his recovery from a knee injury, as well as Munster and Ireland prop Tony Buckley bolstering their pack.
Bennett and Kilroy kicked a brace of penalties each, the former having put Shannon 6-3 up before Kilroy smacked over a fine effort in the 35th minute.
Shannon lost their inside centre John Clogan to a yellow card before half-time (for killing the ball at a ruck) but they made the best possible start to the second half.
The livewire O'Loughlin, who passed a late fitness test to start, scored a splendid try five minutes after the restart.
The Shannon piled forward in a series of drives, hooker Mike Essex then broke off a maul and brought the ball close to the visitors' line before O'Loughlin picked up and speared through a gap to touch down past Cillian O'Boyle.
Bennett missed the conversion But Shannon's tails were up as they looked to gain revenge from last May's 31-6 semi-final defeat by the same opposition.
The influential Kilroy snapped Garryowen back into a 12-11 advantage with two meaty kicks, the second of which was from 50 metres out.
Shannon sneaked ahead again when Bennett split the posts for the third time.
As the game entered the final ten minutes, Geoff Moylan's men, with their pack on song, looked set to grind out the win by keeping it tight.
However, Garryowen managed to create a try out of nothing with some superb counter-attacking which ended with Bourke getting over in the right corner.
The light blues rumbled forward off a midfield lineout, going through two phases with skipper Paul Neville and his back row colleague Conor Hartigan to the fore.
The ball was then moved wide at pace and Kilroy was the link man, up in support to take Andrew Finn out of the game with the pass which put Bourke away.
Crucially, Kilroy could not convert from wide out and Garryowen's efforts were thwarted, four minutes later, when Bennett kept his cool with a shot from in front of the posts.
Prop Buckley, left out of the Munster squad for the game against Sale Sharks on Sunday, shone in a Shannon pack which dominated.
Yet Garryowen did have the best backs on view in Ciaran O'Boyle and the outstanding Kilroy.
Indeed, two great breaks by O'Boyle almost yielded tries but each time the Shannon defence held firm.
SHANNON: Andrew Finn; Richie Mullane, Andrew Thompson, John Clogan, Stephen Kelly; Tadhg Bennett, Fiach O'Loughlin (capt); Gary McNamara, Mike Essex, Tony Buckley, Padraic O'Brien, Fergal Walsh, John O'Connor, Eoghan Grace, David Quinlan.
Replacements used: Emmet McLoughlin for O'Connor, Kevin Griffin for McNamara (both 78 mins).
GARRYOWEN: Conor Kilroy; Lorcan Bourke, Kieran Lewis, Conan Doyle, Ciaran O'Boyle; Alan Kingsley, Cillian O'Boyle; Rory Brosnan, Michael Sherry, Declan Lavery, Mark Melbourne, Frank McKenna, Paul Neville (capt), Conor Hartigan, David Sherry.
Replacements used: Kevin Buckley for M Sherry, Anthony Kavanagh for Hartigan (both 60 mins).
Referee: David Keane (IRFU)