Ulster are through to the quarter-finals of the Heineken Cup after Toulon's 43-20 win over Cardiff.
The result from Pool 2 means that Mark Anscombe’s side, who beat Montpellier yesterday, will, at worst, end the pool stages as one of the two best runners-up.
But they will top Pool 5 and secure a home quarter-final if they win away to Leicester next Saturday (6pm).
Other results today mean that Toulon, Leicester, Clermont and Munster are also through to the knock-out stages.
Live radio coverage of Castres v Leinster on Heineken Cup Special from 12.30 on Sunday 12 January on RTÉ 2fm and RTÉ.ie (Worldwide).