3Com S7906E Configuration Manual page 1148

Share-MDT establishment in a PIM-SM network
Figure 1-6 Share-MDT establishment in a PIM-SM network
BGP: 11.1.3.1/24
PE 1
BGP: 11.1.1.1/24
As shown in Figure 1-6, PIM-SM 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 instance on PE 1 initiates a join to the public network RP, with the share-group address
as the multicast group address in the join message, and a (*, 239.1.1.1) state entry is created on
each device along the path in the public network. At the same time, PE 2 and PE 3 respectively
initiate a similar join process. Finally, an RPT is established in the MD, with the public network RP
as the root and PE 1, PE 2 and PE 3 as leaves.
2) The public instance on PE 1 registers the multicast source with the public network RP, with the
BGP interface address as the multicast source address and the share-group address as the
multicast group address in the register message, and a (11.1.1.1, 239.1.1.1) state entry is created
on each device along the path in the public network. At the same time, PE 2 and PE 3 respectively
initiate a similar register process. Finally, three SPTs between the PE devices and the RP are
established in the MD.
In the PIM-SM network, the RPT, namely the (*, 239.1.1.1) tree, and the three independent SPTs
constitute a share-MDT.
PE 3
RP
P
PE 2
MD
BGP: 11.1.2.1/24
1-8
Share-Group: 239.1.1.1
Public instance BGP peers
RPT (*, 239.1.1.1)
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)