Rugby Celtic Cup quarter-finals/Ulster 23 Leinster 23: The game ended in farce, Ulster's passage to the Celtic League semi-final decided by virtue of having scored three tries to two during the match after extra time failed to produce a winner. John O'Sullivan reports from Ravenhill

The home side will wonder how they only managed parity in normal time, having dominated all bar the opening 25 minutes.

A tremendous performance from their pack underpinned the success, albeit in a game littered with errors. Leinster's young side showed great heart to hang in there, especially Shane Jennings, Brendan Burke and Leo Cullen, but the ridiculous error rate ultimately cost them dearly.

Ulster's facility for frittering away possession in the first half was hugely damaging, compounded by two errors that cost them 14 points. On the first occasion Shane Stewart failed to hold onto Kieron Campbell's flat pass. Leinster centre David Quinlan flipped up the loose ball, Brendan Burke kicked ahead and won the race for possession, and though he kicked the ball sideways, centre Gary Brown was on hand to regather and scoot under the posts.

Leek converted as he would do again on 17 minutes. This time the home side erred fatally when Adam Larkin attempted to chip Leinster scrumhalf Brian O'Riordan just outside his own 22 only for the latter to block the ball and race away to score under the posts.

In between the two tries, Leek had added a penalty to leave the visitors 17-0 ahead. Their rugby hardly merited that advantage.

To their credit, Ulster began to bring a greater precision to their play; the pack started to punch holes, creating the momentum for the backs.

In this respect second rows Matt Mustchin and Matt McCullough were outstanding.

The home side also minced Leinster in the set scrums, quite apart from the 10 minutes that the visitors were without captain Leo Cullen, sent to the sin bin on 29 minutes for handling the ball on the ground close to the Leinster line.

Ulster's domination in this facet of the game was graphically illustrated in the very next scrum, the unequal contest of eight versus seven forwards yielding a penalty try, which Larkin converted. The contest was getting a little tetchy and this boiled over shortly before the interval.

Ulster loose head Ronan McCormack threw three punches in a ruck, the touch judge appeared to single him out and referee Nigel Owens spoke to McCormack and both captains; the upshot was a Leinster penalty. That the Ulster prop was left on the field beggared belief; the least he deserved was a yellow card.

Leek responded with a penalty eight minutes before the interval to leave Leinster 20-7 ahead, a lead they scarcely deserved.

Ulster ripped into Leinster after the restart, the pack, with Matt McCullough, Andy Ward, Roger Wilson and the outstanding Neil Best in the van gave the halfbacks the perfect platform to dictate affairs with Kieron Campbell in particular thriving in the gaps created by the forwards.

Larkin kicked two penalties within five minutes of the restart to bring Ulster back to within seven and for the next 20 minutes they cut through the Leinster pack.

Best was first to cross the visitors' line, on 65 minutes, and three minutes later Tyrone Howe won the race to Campbell's clever chip to nudge his side 23-20 in front.

Leinster second row Ben Gissing was dispatched to the sin bin in between the tries and that appeared to signal his side's demise.

But the visitors somehow survived the pummelling and in doing so demonstrated admirable character for such a young side.

Leek was handed one final opportunity 35 metres out and he calmly posted the penalty, after the home side had been penalised for offside.

With the teams tied at 23-23, it was time for the rulebook and a 15-minute delay as the laws governing extra time were discussed: five minutes each way with the first team to score any points set for a place in the semi-final.

Nobody scored but Ulster march on nevertheless.

SCORING SEQUENCE: 4 mins Brown try, Leek conversion, 0-7; 13 Leek penalty, 0-10; 17 O'Riordan try, Leek conversion, 0-17; 30 penalty try, Larkin conversion, 7-17; 32 Leek penalty, 7-20. Half-time 7-20. 41 Larkin penalty, 10-20; 45 Larkin penalty, 13-20; 65 Best try, 18-20; 68 Howe try, 23-20; 85 Leek penalty, 23-23.

ULSTER: B Cunningham; S Young, R Constable, S Stewart, T Howe; A Larkin, K Campbell; R McCormack, P Shields, B Young; M Mustchin, M McCullough; A Ward (capt), T McWhirter, N Best. Replacements: R Wilson for McWhirter h-time; J Topping for Young 65 mins; R Frost for Mustchin 65 mins; S Shawe for Young 82 mins; S Mallon for Stewart 84 mins.

LEINSTER: G D'Arcy; J McWeeney, G Brown, D Quinlan, B Burke; M Leek, B O'Riordan; J Lyne, G Hickie, E Byrne; B Gissing, L Cullen (capt); A McCullen, D Dillon, S Jennings. Replacements: J Norton for D'Arcy 32 mins; P Coyle for Lyne h-time; N Breslin for Dillon 70 mins; B O'Meara for O'Riordan 72 mins; A Kearney for Gissing 75 mins; J Lyne for Byrne (extra time, 89 mins).

Yellow cards: L Cullen (Leinster) 29-39 mins; B Gissing (Leinster) 65-75 mins.

Referee: N Owens (Wales).