PIM Sparse Device Types

Devices that are configured with PIM Sparse interfaces also can be configured to fill one or more of the following roles:

• PMBR: A PIM device that has some interfaces within the PIM domain and other interface outside the PIM domain. PMBRs connect the PIM domain to the Internet.
• BSR: The Bootstrap Router (BSR) distributes RP information to the other PIM Sparse devices within the domain. Each PIM Sparse domain has one active BSR. For redundancy, you can configure ports on multiple devices as candidate BSRs. The PIM Sparse protocol uses an election process to select one of the candidate BSRs as the BSR for the domain. The BSR with the highest BSR priority (a user-configurable parameter) is elected. If the priorities result in a tie, then the candidate BSR interface with the highest IP address is elected. In the example in the preceding figure, PIM Sparse device B is the BSR. Port 1/2/2 is configured as a candidate BSR.
• RP: The RP is the meeting point for PIM Sparse sources and receivers. A PIM Sparse domain can have multiple RPs, but each PIM Sparse multicast group address can have only one active RP. PIM Sparse devices learn the addresses of RPs and the groups for which they are responsible from messages that the BSR sends to each of the PIM Sparse devices. In the example in the preceding figure, PIM Sparse device B is the RP. Port 1/2/2 is configured as a candidate Rendezvous Point (RP). To enhance overall network performance, the RUCKUS device uses the RP to forward the packets from a group source to the group’s receivers. Later, the RUCKUS device calculates the shortest path between the receiver and source (the Shortest Path Tree, or SPT) and uses the SPT for subsequent packets from the source to the receiver. The RUCKUS device calculates a separate SPT for each source-receiver pair.