4000 Router Series IP Multicast Configuration Guide

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As shown in Figure 46, each C-RP periodically unicasts its advertisement messages (C-RP-Adv messages)

to the BSR. An advertisement message contains the address of the advertising C-RP and the IPv6 multicast

group range to which it is designated. The BSR collects these advertisement messages and organizes the

C-RP information into an RP-set, which is a database of mappings between IPv6 multicast groups and RPs.

The BSR encapsulates the RP-set information in the bootstrap messages (BSMs) and floods the BSMs to

the entire IPv6 PIM-SM domain.

Figure 46 Information exchange between C-RPs and BSR

Based on the information in the RP-set, all routers in the network can select the proper RP for a specific

IPv6 multicast group based on the following rules:

1. The C-RP with the highest priority wins.

2. If all the C-RPs have the same priority, the C-RP with the largest hash value (calculated through the

hash algorithm) wins.

3. If all the C-RPs have the same priority and hash value, the C-RP with the highest IPv6 address wins.

Embedded RP

The embedded RP mechanism enables a router to resolve the RP address from an IPv6 multicast group

address to map the IPv6 multicast group to an RP. This RP can take the place of the configured static RP

or the RP dynamically elected by the bootstrap mechanism. A DR does not need to learn the RP address

beforehand. The process is as follows:

• At the receiver side:

a. A receiver host initiates an MLD report to express its interest in an IPv6 multicast group.

b. After receiving the MLD report, the receiver-side DR resolves the RP address embedded in the

IPv6 multicast group address and sends a join message to the RP.

• At the IPv6 multicast source side:

c. The IPv6 multicast source sends IPv6 multicast traffic to an IPv6 multicast group.

d. The source-side DR resolves the RP address embedded in the IPv6 multicast address, and sends

a register message to the RP.