HP FlexNetwork 7500 Series Configuration Manual page 320

Figure 100 RPT building at the receiver side
As shown in Figure 100, the process for building a receiver-side RPT is the same as the process for
building an RPT in IPv6 PIM-SM:
When a receiver wants to join the IPv6 multicast group G, it uses an MLD message to inform
1.
the directly connected router.
After receiving the message, the router sends a join message, which is forwarded hop by hop to
2.
the RP for the IPv6 multicast group.
The routers along the path from the receiver's directly connected router to the RP form an RPT
3.
branch. Each router on this branch adds a (*, G) entry to its forwarding table.
After a receiver host leaves the IPv6 multicast group G, the directly connected router multicasts a
prune message to all IPv6 PIM routers on the subnet. The prune message goes hop by hop along
the reverse direction of the RPT to the RP. After receiving the prune message, an upstream node
removes the interface that connects to the downstream node from the outgoing interface list. At the
same time, the upstream router checks the existence of receivers for that IPv6 multicast group. If no
receivers for the IPv6 multicast group exist, the router continues to forward the prune message to its
upstream router.
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