Tries from Nick Williams, Jared Payne and Darren Cave, together with eight points from the boot of Ruan Pienaar, saw last season's beaten finalists reach the knockout stages for the third season running.

Ulster were the dominant force in the early stages but it took 20 minutes to claim their first try when Williams powered over from close-range. The former Munster and Aironi No8 claimed his seventh score of the season by bludgeoning his way through Moray Low and Rob Harley from five metres out.

Pienaar defied the wet weather to add a well-taken conversion to his sixth-minute penalty as Ulster moved 10 points clear of their Scottish rivals with a quarter of the game gone.

Glasgow worked their way back into the encounter despite a dominant Ulster scrum and Duncan Weir missed a brace of penalty chances in the closing stages of the half after Pienaar had failed with one attempt himself after 27 minutes.

Weir got the Warriors on the board eight minutes after the break but, despite a 52nd-minute yellow card for Ulster flanker Iain Henderson and a better showing in terms of territory and possession, Glasgow could only add a further three points from the fly-half to their tally in the remainder of the match.

Instead it was the hosts who pushed on, with Payne stepping inside DTH van der Merwe with a clever dummy from just a few metres out after 73 minutes.

Pienaar was off target with the extras but had added an earlier penalty and Ulster were 18-6 to the good and effectively home and dry.

Cave then supplied some gloss to the end result with a fine finish from 40 metres out with less than two minutes remaining but Ulster couldn't find the bonus-point try that would have enhanced their hopes of a home tie in April.