HP MSR2000/3000/4000 Router Series IP Multicast Configuration Guide

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interface of the packet as the incoming interface of the forwarding entry. After the router receives an IPv6
multicast packet, it searches its IPv6 multicast forwarding table:
• If no forwarding entry matches the packet, the packet undergoes an RPF check. The router creates
an IPv6 multicast routing entry with the RPF interface as the incoming interface and installs the entry
into the IPv6 multicast forwarding table.
{ If the interface that received the packet is the RPF interface, the RPF check succeeds and the
router forwards the packet out of all outgoing interfaces.
{ If the interface that received the packet is not the RPF interface, the RPF check fails and the router
discards the packet.
• If a forwarding entry matches the packet, and the interface that received the packet is the incoming
interface of the forwarding entry, the router forwards the packet out of all outgoing interfaces.
• If a forwarding entry matches the packet, but the interface that received the packet is not the
incoming interface of the forwarding entry, the IPv6 multicast packet undergoes an RPF check.
{ If the RPF interface is the incoming interface, it indicates that the forwarding entry is correct but
the packet traveled along a wrong path. The router discards the packet.
{ If the RPF interface is not the incoming interface, it indicates that the forwarding entry has
expired, and the router replaces the incoming interface with the RPF interface. If the interface
that received the packet is the RPF interface, the router forwards the packet out of all outgoing
interfaces. Otherwise, it discards the packet.
Figure 37 RPF check process
As shown in Figure 37, assume that IPv6 unicast routes are available in the network, and IPv6 multicast
packets travel along the SPT from the multicast source to the receivers. The IPv6 multicast forwarding table
on Router C contains the (S, G) entry, with Ethernet 1/2 as the RPF interface.
• When Ethernet 1/2 of Router C receives an IPv6 multicast packet, because the interface is the
incoming interface of the (S, G) entry, the router forwards the packet out of all outgoing interfaces.
• When Ethernet 1/1 of Router C receives an IPv6 multicast packet, because the interface is not the
incoming interface of the (S, G) entry, the router performs an RPF check on the packet. The router
searches its IPv6 unicast routing table and finds that the outgoing interface to the source (the RPF
interface) is Ethernet 1/2. This means that the (S, G) entry is correct but the packet traveled along
a wrong path. The RPF check fails and the router discards the packet.
Receiver
Receiver
Source
2000::101/16
Router A
Router B
Router C
Eth1/2
Eth1/1
Eth1/1
IPv6 Multicast packets
Destination/Prefix
IPv6 Routing Table on Router C
2000::/16
Interface
Eth1/2