Configure routers as candidate bootstrap routers (C-BSR) to provide backup protection in case the primary BSR fails. PIM-SM cannot operate without a BSR. A PIM-SM domain can use only one active BSR.
The C-BSR with the highest configured priority becomes the BSR for the domain. If two C-BSRs use equal priority, the candidate with the higher IP address becomes the BSR. If you add a new C-BSR with a higher priority to the domain, it automatically becomes the new BSR.
The C-BSR with the highest BSR-preference and address becomes the active BSR. The default is –1, which indicates that the current interface is not a C-BSR.