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As shown in
, 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 network 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
separately 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 network on PE 1 registers the multicast source with the public network RP and the
public network RP initiates a join to PE 1. With the BGP interface address as the multicast
source address and the share-group address as the multicast group address, 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 separately 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.
Share-MDT establishment in a BIDIR-PIM network
Figure 77 Share-MDT establishment in a BIDIR-PIM network
As shown in
, BIDIR-PIM 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 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) entry is
created on each device along the path in the public network. At the same time, PE 2 and PE 3
separately initiate a similar join process. Finally, the receiver-side 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 network on PE 1 sends multicast data, with the share-group address as the
destination multicast group address. The DF on each subnet that the multicast data travels
through in the public network unconditionally forwards the data to the RP, and a (*, 239.1.1.1)
entry is created on each device along the path. At the same time, PE 2 and PE 3 separately
initiate a similar process. Finally, the source-side RPT is established in the MD, with PE 1, PE 2,
and PE 3 as the roots and the public network RP as the leave.
In the BIDIR-PIM network, the receiver-side RPT and the source-side RPT constitute a bi-directional
RPT (the (*, 239.1.1.1) tree), which is a share-MDT.
