HP FlexNetwork 7500 Series Configuration Manual page 198

A flood-prune process (in PIM-DM) or a join process (in PIM-SSM) is initiated across the
public network to establish an SPT across the public network.
•
If the VPN network runs PIM-SM:
Hello packets are forwarded through MTI interfaces to establish PIM neighboring
relationships.
If the receivers and the VPN RP are in different sites, a join process is initiated across the
public network to establish an RPT.
If the multicast source and the VPN RP are in different sites, a registration process is
initiated across the public network to establish an SPT.
NOTE:
PIM mode must be the same for all interfaces that belong to the same VPN, including those
interfaces that are bound with the VPN instance and the MTI interfaces on PE devices.
As shown in Figure 67:
•
PIM-SM is running in both the public network and the VPN network.
•
Receiver for the VPN multicast group G (225.1.1.1) in Site 2 is attached to CE 2.
•
CE 1 of Site 1 acts as the RP for group G (225.1.1.1).
•
The default-group address used to forward public network data is 239.1.1.1.
Figure 67 Transmission of multicast protocol packets
Source
RP
CE 1
Site 1
S: 192.1.1.1/24
G: 225.1.1.1
Default-group: 239.1.1.1
The multicast protocol packet is delivered as follows:
Receiver sends an IGMP report to CE 2 to join the multicast group G. CE 2 creates a local state
1.
entry (*, 225.1.1.1) and sends a join message to the VPN RP (CE 1).
After receiving the join message from CE 2, the VPN instance on PE 2 creates a state entry (*,
2.
225.1.1.1) and specifies the MTI interface as the upstream interface. The VPN instance on PE
2 considers the join message to have been sent out of the MTI interface, because step 3 is
transparent to the VPN instance.
PE 2 encapsulates the join message into a public network multicast data packet (11.1.2.1,
3.
239.1.1.1) by using the GRE method. In this multicast data packet, the source address is the
MD source interface IP address 11.1.2.1, and the destination address is the default-group
address 239.1.1.1. PE 2 then forwards this packet to the public network.
BGP: 11.1.3.1/24
PE 3
P
PE 1
MD
BGP: 11.1.1.1/24
188
CE 2
PE 2
BGP: 11.1.2.1/24
Public instance BGP peers
VPN instance join (*, 225.1.1.1)
Public instance join (11.1.2.1, 239.1.1.1)
Receiver
Site 2