Two-time European Cup champions Munster reached the quarter-finals for the 13th time on Saturday with a battling 26-10 win over Castres to clinch a fifth victory in five Pool One matches this season.
After missing out on the knockout rounds last season, the Irish side became the first side to make the quarter-finals this time around with a gritty win over the French outfit who are now out of contention.
Johne Murphy gave Munster an eighth-minute lead with a try while Ronan O'Gara kicked the conversion and three penalties for a 16-7 interval advantage although a Yannick Caballero try kept Castres in touch.
But South African loosehead prop Wian du Preez then ensured victory with a 68th-minute try -- his first in the competition -- with O'Gara again hitting the extras.
Northampton, the 2000 champions, recovered from a 14-6 half-time deficit to beat Scarlets 29-17 to move into second place in the pool, eight points behind Munster.
Four-time champions Toulouse clinched a four-try, bonus-point 24-3 win over Connacht to extend their lead at the top of Pool Six to six points over Harlequins who meet Gloucester later Saturday.
Toulouse and Harlequins clash next weekend in the final round of pool matches.
Louis Picamoles, Maxime Medard and a double from Fijian winger Timoci Matanavou gave the French giants victory.
In Pool Two, Cardiff Blues beat London Irish in Reading with Welsh skipper Sam Warburton grabbing the only try of the game early in the second half.
The win moved Cardiff to 17 points, the same as Edinburgh who had needed a last-minute drop goal from replacement fly-half Phil Godman to secure a 27-24 win over Racing Metro on Friday.
In Pool Four, Clermont ran in 12 tries in a 82-0 rout of hapless Italian side Aironi to move to 16 points, three behind Ulster, who trounced double-champions Leicester 41-7 on Friday.
Clermont and Ulster will meet in France next weekend in the final round of matches, a game which will decide top spot in the section.
All Blacks winger Sitiveni Sivivatu grabbed a hat-trick of tries for Clermont as did fellow winger and Fench international Julien Malzieu.
Welsh full-back Lee Byrne scored two as did lock forward Alexandre Lapandry.
Australian fly-half Brock James scored a try and was seven for seven in conversions while back-row forward Elvis Vermeulen completed the rout.
Defeat left the Italians without a point fron their five matches.