3Com MSR 50 Series Configuration Manual page 1288

1288 C 75: M
HAPTER ULTICAST
c
n
VPN C
ONFIGURATION
CAUTION: All interfaces that belong to the same VPN, including those interfaces
with VPN instance bindings and the MTI on PE devices, must run the same PIM
mode.
1 If PIM-DM is running in the VPNs network, a flood-prune process needs to be
initiated across the public network to create SPTs.
2 On a VPNs network running PIM-SM:
If the receivers and the VPN RP are in different sites, joins need to be initiated
■
across the public network to establish an RPT.
If the multicast source and the VPN RP are in different sites, registrations need
■
to be initiated across the public network to establish SPTs.
The following example explains how multicast protocol packets are transmitted
based on the share-MDT while PIM-SM is running in both the public network and
the VPNs network and the receivers and the VPN RP are in different sites.
As shown in Figure 374, PIM-SM is running in both the public network and the
VPNs network, Receiver in Site 2 is attached to CE 2, while CE 1 of Site 1 acts as
the RP for VPN multicast group G (225.1.1.1).
Figure 374 Transmission of multicast protocol packets
Source
RP
CE 1
S: 192.1.1.1/24
G: 255.1.1.1
Share-Group: 239.1.1.1
The work process of multicast protocol packets is as follows:
1 Receiver sends an IGMP membership report for multicast group G to CE 2. CE 2
creates a local (*, 225.1.1.1) state entry and sends a join message to the VPN RP
(CE 1).
2 Upon receiving the join message from CE 2, the VPN instance on PE 2 creates a (*,
225.1.1.1) state entry with the upstream interface being the MTI, and passes the
join message to the device for further processing. Now, the VPN instance on PE 2
considers that the join message has been sent out the MTI.
3 PE 2 encapsulates the join message by means of Generic Routing Encapsulation
(GRE), with its IBGP interface address as the multicast source address and the
IBGP: 11 .1.3.1/24
PE 3
P
PE 1
MD
IBGP : 11.1.1 .1/24
PE 2 CE 2
IBGP : 11.1.2.1 /24
Public instance IBGP peers
VPN instance join (*, 255.1.1.1)
Public instance join (11.1.2.1, 239.1.1.1)
Receiver