228
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.
Share-MDT establishment in a PIM-SM network
Figure 64
Share-MDT establishment in a PIM-SM network
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 on the public network.
2.
At the same time, PE 2 and PE 3 initiate a similar join process, respectively.
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.
3.
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 on the public network.
4.
At the same time, PE 2 and PE 3 initiate a similar register process, respectively.
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.
Public instance BGP peers
RPT (*, 239.1.1.1)
MD
P
RP
PE 3
PE 2
PE 1
BGP: 11.1.2.1/24
BGP: 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
