Racing seal Top 14 semi-final spot, Lyon & Castres in play-offs
Racing 92 thrashed Agen 42-13 to ensure they claimed second place in Top 14 and an automatic place in the semi-finals, while Castres thrashed Oyonnax to seal the last spot in the play-offs.
The European Champions Cup finalists ran in six tries, including a double from Juan Imhoff, and scored 21 unanswered points to pull away from the visitors, who had initially kept things tight.
Ole Avei, Manuel Carizza, Edwin Maka and So'otala Fa'aso'o also crossed for rampant Racing, with Benjamin Dambielle nailing every conversion as they joined Montpellier as confirmed participants in the last four.
Toulouse had been hoping to get into the top two, but they were beaten 36-26 by last season's champions Clermont Auvergne, who paid tribute to retiring captain Aurelien Rougerie with a guard of honour.
Castres came into Saturday in possession of the sixth and final play-off spot and made sure they held on to it with an emphatic 54-3 win over Oyonnax.
Five of the hosts' seven tries came inside the final 19 minutes, with Steve Mafi scoring twice as Castres booked a quarter-final contest against Toulouse.
The defeat means Oyonnax will contest the relegation play-offs and ensured Stade Francais avoid that fate despite losing 31-7 at La Rochelle, a result that was not enough to get the victors into the top six.
Lyon also made certain of their own progression to the play-offs, the fifth-place side beating top leaders Montpellier 32-24 after coming from behind with 10 points in the final nine minutes, Xavier Mignot's try clinching the victory.
They will meet Toulon, who suffered a 38-26 loss to Pau that was proved insufficient to keep the hosts' top-six aspirations alive.
Relegated Brive ended their stay in the top flight on a high, beating 14-man Bordeaux-Begles 22-20 courtesy of a penalty try after regulation time had expired.