H3C Technologies H3C S10500 Series Switches - Manual (Page 27)

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incoming interface. The result of the RPF check determines whether the packet will be forwarded or
discarded. The RPF check mechanism is the basis for most multicast routing protocols to implement
multicast forwarding.
NOTE:
For more information about the RPF mechanism, see the chapters “Multicast routing and forwarding
configuration”
and “IPv6 multicast routing and forwarding configuration.”
Multi-instance multicast
NOTE:
Multi-instance multicast is not available in IPv6 networks.
Multi-instance multicast refers to multicast in Multiprotocol Label Switching (MPLS) Layer 3 virtual private
networks (L3VPNs).
Introduction to the multi-instance concept
VPN networks must be isolated from one another and from the public network. As shown in Figure 10 ,
VPN A and VPN B separately access the public network through PE devices.
Figure 10 Networking diagram for MPLS L3VPN
• The P device belongs to the public network. The CE devices belong to their respective VPNs. Each
CE device serves its own network and maintains only one set of forwarding mechanisms.
• The PE devices connect to the public network and the VPN networks at the same time. Each PE
device must strictly distinguish the information for different networks, and must maintain a separate
forwarding mechanism for each network. On a PE device, a set of software and hardware that
serves the same network forms an instance. Multiple instances exist on a PE device at the same time,