H3C S7500 Series Operation Manual page 481

Operation Manual – Multicast
H3C S7500 Series Ethernet Switches
The BSR is the core management device in a PIM-SM network. The BSR is responsible
for:
Collecting the Advertisement messages sent by the Candidate-RP (C-RP) in the
network.
Selecting part of the C-RP information to constitute the RP-set, namely, the
mapping database between the multicast group and RP.
Advertising the RP-set to the whole network in order that all the routers (including
the DR) in the network know the position of the RP.
One or more candidate BSRs must be configured in a PIM domain. Through the
auto-election, the candidate BSRs elect a BSR which is responsible for collecting and
advertising RP information. The auto-election among candidate BSRs is described in
the following section:
Specify a PIM-SM-enabled interface when configuring a router as a candidate
BSR.
Each candidate BSR considers itself as the BSR of the PIM-SM network and uses
the IP address of the specified interface as the BSR address to send Bootstrap
messages.
When the candidate BSR receives Bootstrap messages from other routers, it will
compare the BSR address in each received Bootstrap message with its own BSR
address in priority and IP address. When the priority is the same, the candidate
BSR with a higher IP address is considered to be better. If the former is better, the
candidate BSR will replace its own BSR address with the new BSR address and
does not consider itself as BSR any more. Otherwise, the candidate BSR will keep
its own BSR address and continue to consider itself as BSR.
The positions of RPs and BSRs in the network are as shown in
Figure 7-4 Diagram for the communication between RPs and BSR
C-RP
BSR message
Advertisement message
PIM-SM
BSR
C-RP
C-BSR
C-RP
7-7
Chapter 7 PIM Configuration
Figure 7-4:
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