Routing groups are usually configured at the [edit routing-instances instance-name routing-options] hierarchy level. However, with multicast in VRF instances, you must configure routing groups differently. Configure the multicast routing group by adding the rib-groups statement at the [edit routing-options] hierarchy level.
After you configure the multicast routing group in the main routing instance, add the routing group to the VPN's VRF instance. To do this, include the rib-group statement at the [edit routing-instances instance-name protocols pim] hierarchy level.
For a multicast for Layer 3 VPN example, see Example: Configuring PIM Sparse Mode over Layer 3 VPNs.