Ulster 23-23 Leinster
Ulster (7) 23
Tries: Penalty-try, Best, Howe
Pens: Larkin 2
Leinster (20) 23
Tries: Brown, O'Riordan
Cons: Leek 2
Pens: Leek 3
A superior try-count earned Ulster a place in the Celtic Cup semi-finals at Leinster's expense after extra-time had failed to separate the teams.
An injury-time penalty by Leinster fly-half Matt Leek brought the match into extra-time.
Earlier, the visitors had capitalised on errors to notch two first half tries which left them 20-7 ahead at the break.
However, Alan Solomons' side cut out the mistakes after the break to dominate the second period and final quarter tries by Neil Best and Tyrone Howe seemed to have earned the verdict in normal time before Leek's last ditch penalty.
Leinster made a dream start by notching a breakaway try in the third minute after Shane Stewart had failed to grasp a wild pass in midfield from Kieran Campbell.
David Quinlan kicked the ball ahead and looked likely to score the try himself but eventually his fellow-centre Gary Brown grabbed the possession and crossed underneath the Ulster posts. Matt Leek added the conversion.
The visitors continued to dominate and Leek then added a 13th minute penalty to extend their lead to 10-0.
Things then went from bad to worse for the home side when an attempted chip ahead by fly-half Adam Larkin in his own half was easily gathered by Leinster scrum-half Brian O'Riordan who had the simple task of running through for the touchdown.
Leek's conversion left Leinster 17-0 ahead after only 16 minutes.
Ulster then produced a period of sustained pressure which eventually yielded a 29th minute penalty-try shortly after Leo Cullen had been sin-binned for illegal handling in a ruck.
Ulster's Shane Stewart attempts a break
Larkin's conversion cut Leinster's lead to 10 points.
However, almost straight from the re-start, Matt Mustchin was caught offside in his own '22 and Leek had no difficulty adding the three points for the visitors.
Leinster then lost Irish international full-back Gordon D'Arcy because of injury with James Norton introduced.
Thirteen points down at the break, Ulster needed quick scores in the second period and a Adam Larkin penalty boosted the home side in the 43rd minute.
A further long-range Larkin penalty in the 47th minute left Leinster only seven ahead.
Andy Ward seemed certain to have scored Ulster's second try a minute later after charging over the Leinster line but he failed to ground the ball.
Ulster continued to dominate and Ben Gissing became the second Leinster forward to be sin-binned when he was cautioned in the 64th minute.
Matt Muschin won the resulting line-out and set up a drive which culminated with Neil Best crashing over for the try.
Larkin missed the conversion but Ulster, at only two points adrifit, were definitely in the ascendancy with 15 minutes left.
Within four minutes, the home side were ahead with wing Tyrone Howe notching the try in the corner after a clever kickahead by Campbell.
Ulster continued to control the exchanges and seemed certain to claim a win in normal time.
However deep into injury time Leinster burst into the Ulster half and a silly offside indiscretion by Ronan McCormack enabled Matt Leek to bring the match into extra-time with a 35-metre penalty.
Confusion reigned as to the format for extra-time before it was eventually ascertained that the match would be decided by a golden score during the two five-minute periods.
The two periods failed to produce a score but Ulster's extra try proved enough to earn a countback win.
Ulster: B Cunningham; S Young; R Constable, S Stewart, T Howe; A Larkin, K Campbell; R McCormack, P Shields, B Young; M McCullough, M Mustchin; A Ward (capt), N Best, T McWhirter.
Replacements: R Spee, S Mallon, J Topping, S Shawe, N Brady, R Wilson, R Frost
Leinster: G D'Arcy, J McWeeney, G Brown, D Quinlan, B Burke, M Leek, B O'Riordan, J Lyne, G Hickie, E Byrne, L Cullen (capt), B Gissing, A McCullen, S Jennings, D Dillon.
Replacements: P Coyle, D Blaney, A Kearney, N Breslin, B O'Meara, J Downey, J Norton.