Clermont go top in France
Clermont are now the only undefeated team in the Top 14 after England wing David Strettle scored two second-half tries to lead his side home.
Remi Lamerat, Paul Jedrasiak and Georgian prop Davit Zirakashvili also crossed with veteran scrumhalf Morgan Parra kicking 15 points.
Saturday's win followed last week's impressive 47-10 rout of champions Racing 92.
"Today perhaps wasn't as attractive or spectacular as last week but the weather conditions could explain that," said Clermont 
skipper Parra after the win secured in heavy rain.
"But we told ourselves that we needed to win our first two home matches and we have done that with our attacking game proving to be the key. Job done."
Clermont have a two-point lead over La Rochelle who suffered their first defeat of the season at Brive despite dominating the first half where they ran in tries from Steeve Barry, Kini Murimurivalu and Vincent Rattez.
But Brive hit back after the interval with Arnaud Mignardi scoring a try to add to Benjamin Lapeyre's first-half effort.
The reliable boot of Gaetan Germain proved crucial with two conversions and five penalties. La Rochelle at least went home with a losing bonus under their belts.
Toulouse old boy Frederic Michalak punished his former club by scoring six penalties and a conversion as promoted Lyon won 25-20.
It was a third straight defeat for a Toulouse side who lost to Toulon and Racing in their last two games.
"We needed a good win against a big team," said Lyon coach Pierre Mignoni. "But my word that was a tough match."
The 33-year-old flyhalf Michalak spent 10 years over two spells at Toulouse but piled on the agony against his old club, helping promoted Lyon to a 10-0 lead with just 12 minutes gone.
Mignoni felt vindicated on his surprise signing finally coming good.
"I was criticised for signing him but today you saw how valuable he is," he said.
Fijian wingr Napolioni Nalaga used brute force to burst through to score Lyon's only try after eight minutes and Michalak added the conversion and four penalties to send Lyon in 19-3 up at the break.
The man who won 77 caps for France was on fire when playing his fifth game for Lyon, whose second row Taïasina Tuifua's relentless cover tackling was also key in undoing Toulouse.
After the break Toulouse bounced back and scored two converted tries and a penalty with Lyon only responding with two penalties.
"We have beaten a very big side and we will beat others too," said Michalak.
Toulouse coach Ugo Mola expressed frustration at his side's failure to convert possession into points.
"We are a much better side than what you might think looking at the 19 points we conceded in the first half and we'll go away, get our heads down and work it out," he said
Their second half tries came from wingers Sofiane Guitoune in the 48th minute and Paul Lusi Perez just after the hour, as Toulouse came within five points of Lyon at 22-17.
But hopes of victory evaporated when suddenly they were down to 13 men as Census Johnston on 65 minutes and Edwin Maka on 67 were yellow-carded and sat out the best part of the rest of the game.
Elsewhere on Saturday, Pau stunned 2015 champions Stade Francais 23-6 with their All Blacks imports playing crucial roles.
Centre Conrad Smith scored an 11th minute try while fly-half Colin Slade converted that effort as well as Steffon Armitage's 45th-minute score.
Slade also slotted over three penalties as Pau recovered well from their 13-41 mauling at the hands of Montpellier last time out.
Agence France-Presse
