And Clermont took advantage of their chance to close up on the league leaders, taking charge of the match with tries from Napolioni Nalaga and Sivivatu Sitiveni, while Grenoble needed a late try from Jonathan Pelissié to grab a losing bonus point.
Toulouse thumped Bayonne 42-6 to keep their stranglehold on third place, four points behind Clermont.
Fifth-placed Montpellier edged a 15-13 victory over Bordeaux-Belges in a dramatic finish.
Bordeaux had a great chance at an away win as Metuisela Talebulamaijaina's try 11 minutes from full time put them one point ahead, but Benoît Paillaugue's penalty six minutes from time saw Montpellier home.
Racing Metro won their fifth consecutive victory in the Top 14 as they won 23-11 away at Biarritz, a run which has lifted them to sixth place in the table.
Snowy conditions made play difficult, match Manuel Carizza and Sébastien Descons scored tries for Racing Metro.
Jonathan Wisniewski's four successful shots at goal and Fabrice Estebanez's drop goal completed the scores for Racing Metro, while Biarritz's efforts were flatted by a late Dimitri Yachvili penalty and Thibault Dubarry try.
Agen beat Mont-de-Marsan 9-3, while Perpignan beat Stade Francais 32-16 in the late match on Saturday night thanks to two tries from Alisona Taumalolo and one each from Luke Narraway and Armand Battle.