H3C Technologies H3C S12500-X Series Switches - Manual (Page 161)

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RPT building
Figure 48 RPT building in an IPv6 PIM-SM domain
As shown in Figure 27 , the process of building an RPT is as follows:
1. When a receiver wants to join the IPv6 multicast group G, it uses an MLD message to inform the
receiver-side DR.
2. After getting the receiver information, the DR sends a join message, which is forwarded hop by
hop to the RP for the IPv6 multicast group.
3. The routers along the path from the DR to the RP form an RPT branch. Each router on this branch
adds to its forwarding table a (*, G) entry, where the asterisk (*) represents any IPv6 multicast
source. The RPT is rooted at the RP and has the DR as its leaf.
When the IPv6 multicast data addressed to the IPv6 multicast group G reaches the RP, the RP forwards
the data to the DR along the established RPT, and finally to the receiver.
When a receiver is no longer interested in the IPv6 multicast data addressed to the IPv6 multicast group
G, the receiver-side DR sends a prune message, which goes hop by hop along the RPT to the RP. After
receiving the prune message, the upstream node deletes the interface that connects to this downstream
node from the outgoing interface list and checks whether it has receivers for that IPv6 multicast group. If
not, the router continues to forward the prune message to its upstream router.
IPv6 multicast source registration
The IPv6 multicast source uses the registration process to inform an RP of its presence.