avoid business disruption. Similarly, several C-RPs can be configured in one PIM SM domain,
and each multicast group’s corresponding RP can be calculated through the BSR mechanism.
The location of RP and BSR in the network is shown below:
Figure 11-14 The Locations of C-RP, C-BSR and BSR
RPT Building
Figure 11-15 RPT Topology in PIM SM
As shown in Figure 11-17, the establishing process of RPT is illustrated below:
(1)
When a receiver joins a multicast group G, it informs the directly connected DR with IGMP
message;
(2)
After receiving the IGMP message from multicast group G, the DR sends PIM join message
toward the corresponding root, also known as the RP;
(3)
The join message travels router-by-router toward the root, constructing a branch of the
RPT as it goes. These routers generate (*, G) entries in their forwarding tables with *
representing any multicast source. The RPT works with RP as the root node, and DR as the
branch node.
278
