R3303-HP HSR6800 Routers IP Multicast Configuration Guide

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transmittion of the VPN data over the public network. However, the multicast data transmission process
(the MDT transmission process) over the public network is very complicated.
Share-MDT establishment
The multicast routing protocol running on the public network can be PIM-DM, PIM-SM, BIDIR-PIM, or
PIM-SSM. The process of creating a share-MDT is different in these PIM modes.
Share-MDT establishment in a PIM-DM network
Figure 66 Share-MDT establishment in a PIM-DM network
As shown in Figure 66, PIM-DM is enabled in the network and all the PE devices support VPN instance
A. The process of establishing a share-MDT is as follows:
1. The public network on PE 1 initiates a flood-prune process in the entire public network, with the
BGP interface address (namely the interface address used to establish the BGP peer) as the
multicast source address and the share-group address as the multicast group address.
All the other PE devices that are running VPN instance A are group members, so that a (11.1.1.1,
239.1.1.1) state entry is created on each device along the path on the public network. This forms
an SPT with PE 1 as the root, and PE 2 and PE 3 as leaves.
2. At the same time, PE 2 and PE 3 initiate a similar flood-prune process, respectively.
Finally, three independent SPTs are established in the MD. In the PIM-DM network, these
independent SPTs constitute a share-MDT.
Public network BGP peers
MD
P
PE 3
PE 2PE 1
BGP: 11.1.2.1/24BGP: 11.1.1.1/24
SPT (11.1.1.1, 239.1.1.1)
SPT (11.1.2.1, 239.1.1.1)
SPT (11.1.3.1, 239.1.1.1)
BGP: 11.1.3.1/24
Share-Group: 239.1.1.1