After the primary path is recovered, the P2MP LSP switches back to the primary path and away from the protection next-hop (FRR). This switch back to primary may cause a brief traffic outage.
The replication SID next-hops send optimistic ARP to populate the ARP table. If the next-hop MAC address is not found in the ARP table (that is, the address is not populated by BFD, IGP, or any other packet), the optimistic ARP populates the ARP table. The reversion from FRR to the primary next-hop happens only if the primary path ARP entry is found in the ARP table.