Joey Carbery stepped up in the absence of Johnny Sexton as Leinster started their Champions Cup campaign with a bonus point 24-17 win over French powerhouse Montpellier at the RDS in Dublin.

Playing at fullback, the 21-year-old was a constant threat with ball in hand, scoring one try and making several clean breaks to cause the visitors all sorts of problems in defence.

Carbery's try from Leinster was followed by one from openside Josh van der Flier which gave the home side a 12-0 lead.

Montpellier looked threatening through their monster winger Nemani Nadolo who scored the first of his two tries just before the break to reduce Leinster's lead to five points at half-time.

Robbie Henshaw -- another star performer for the home side -- latched onto a loose ball from a Ross Byrne cross-field kick to score Leinster's third to restore a 12 point lead.

Nadolo scored his second to give Montpellier a sniff in the latter stages of the second half but Barry Daly responded immediately with Leinster's bonus point score.

A Ruan Pieenar penalty brought the gap back to seven points, and Leinster were forced to defend stoically in the final stages as Adam Byrne was shown a yellow card for a failed interception.

But the visitors -- coached by former Scotland boss Vern Cotter -- failed to make the most of the numerical advantage as Leinster held on for victory while Montpellier picked up a losing bonus point.