256
2.
When PIM-SM is running in the VPN:
{
Before SPT switchover, if the multicast source and the VPN RP are in different sites, the
multicast source forwards VPN multicast data to the VPN RP along the VPN SPT across the
public network. If the VPN RP and the receiver are in different sites, the VPN RP forwards
VPN multicast traffic to the receiver along the VPN RPT over the public network.
{
After SPT switchover, if the multicast source and the receiver are in different sites, the
multicast source forwards VPN multicast data to the receiver along the VPN SPT across the
public network.
3.
When BIDIR-PIM is running in the VPN, if the multicast source and the VPN RP are in different
sites, the multicast source sends multicast data to the VPN RP across the public network along
the source-side RPT. If the VPN RP and the receivers are in different sites, the VPN RP
forwards the multicast data to the receivers across the public network along the receiver-side
RPT.
For more information about RPT-to-SPT switchover, see "
"
The following example explains how multicast data packets are delivered based on the share-MDT
when PIM-DM is running in both the public network and the VPN network.
As shown in
, PIM-DM is running in both the public network and the VPN sites, Receiver of
the VPN multicast group G 225.1.1.1 in Site 2 is attached to CE 2, and Source in Site 1 sends
multicast data to multicast group G); the share-group address used to forward public network
multicast data is 239.1.1.1.
Figure 80 Delivery of multicast data packets
The VPN multicast traffic is delivered across the public network as follows.
1.
Source sends customer multicast data (192.1.1.1, 225.1.1.1) to CE 1.
2.
CE 1 forwards the VPN multicast data along an SPT to CE 1, and the VPN instance on PE 1
checks the MVRF. If the outgoing interface list of the forwarding entry contains an MTI, PE 1
processes the VPN multicast data. Now, the VPN instance on PE 1 considers that the VPN
multicast data has been sent out the MTI.
3.
PE 1 encapsulates the multicast data by means of GRE, with its BGP interface address as the
multicast source address and the share-group address as the multicast group address, to
convert it into a normal, public network multicast data packet (11.1.1.1, 239.1.1.1). PE 1 then
forwards it to the public network.
4.
The multicast data packet (11.1.1.1, 239.1.1.1) is forwarded to the public network on all the PE
devices along the share-MDT. After receiving this packet, every PE device de-encapsulates it
