When you restart PIM, the following tasks are performed: The PIM database is deleted. The MRIB and MFIB are unaffected and forwarding of traffic continues. The multicast route ownership is verified through the MRIB. Periodic PIM join and prune messages from neighbors are used to repopulate the database. https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus9000/sw/6-x/multicast/configuration/guide/b_C