Инструкции По Установке для 3com S7906E

 

1-9 

Figure 1-7 Shart-MDT establishment in a PIM-SSM network 

 

Public instance BGP peers

P

PE 3

PE 2

PE 1

BGP: 11.1.2.1/24

BGP: 11.1.1.1/24

SPT (11.1.1.1, 232.1.1.1)

SPT (11.1.2.1, 232.1.1.1)

SPT (11.1.3.1, 232.1.1.1)

BGP: 11.1.3.1/24

Share-Group: 232.1.1.1

 

As shown in 

, PIM-SSM is enabled in the network and all the PE devices support VPN 

instance A. The process of establishing a share-MDT is as follows:  

The public instance on PE 1 sends the local BGP MDT routing information, including its BGP interface 

address and the share-group address, to PE 2 and PE 3. PE 2 and PE 3 perform the same operation to 

exchange their BGP MDT routing information with one another. Upon receiving the BGP MDT 

information from PE1, PE 2 and PE 3 respectively send a subscribe message for channel subscription 

hop by hop toward the BGP interface of PE1. A (11.1.1.1, 232.1.1.1) entry is created on devices on the 

path toward PE 1 in the public network. Thus an SPT is created in the network, with PE 1 as its root, PE 

2 and PE 3 as its leaves.  

At the same time, PE 2 and PE 3 respectively initiate a similar SPT establishment process. Finally, three 

independent SPTs are established in the MD. In the PIM-SS M network, the three independent SPTs 

constitute a share-MDT.  

As discussed above, a share-MDT is characterized as follows, no matter what PIM mode is running in 

the public network: 

z 

All PE devices that support this VPN instance join the share-MDT.  

z 

All VPN multicast packets that belong to this VPN, including protocol packets and data packets, are 

forwarded along the share-MDT to every PE device in the public network, even if they have no 

active receivers downstream.  

A share-MDT can be used for delivering multicast packets, including both multicast protocol packets 

and multicast data packets. However, the transmission processes for these two types of multicast 

packets are different. 

When a multicast source and the receivers are located in different sites of a VPN, multicast protocol 

packets must be transmitted across the public network. Protocol packets are encapsulated into normal 

multicast data packets for the public network on the local PE device, transmitted along the share-MDT,