BSR configuration and election
There should be multiple BSR candidates configured in a PIM-SM domain so that if the elected BSR becomes unavailable, another router will take its place. In the BSR election process, the BSR candidate configured with the highest priority number is selected. Where the highest priority setting is shared by multiple candidates, the candidate having the highest IP address is selected. In the event that the selected BSR subsequently fails, another election takes place among the remaining BSR candidates. To facilitate a predictable BSR election, configure a higher priority on the router you want elected as the BSR for the domain.
A router serving as the BSR for a domain should be central to the network topology. This helps to ensure optimal performance and also reduce the possibility of a network problem isolating the BSR.