H3C Technologies H3C S10500 Series Switches - Manual (Page 335)

320
3. If the corresponding (S, G) entry exists, but the interface that received the packet is not the
incoming interface in the IPv6 multicast forwarding table, the IPv6 multicast packet undergoes an
RPF check.
○ If the RPF interface is the incoming interface of the (S, G) entry, this means the (S, G) entry is
correct but the packet arrived from a wrong path. The packet will be discarded.
○ If the RPF interface is not the incoming interface, this means that the (S, G) entry has expired,
and the router replaces the incoming interface with the RPF interface. If the interface on which
the packet arrived is the RPF interface, the router forwards the packet to all the outgoing
interfaces. Otherwise it discards the packet.
Assume that IPv6 unicast routes are available in the network, IPv6 MBGP is not configured, and IPv6
multicast packets travel along the SPT from the multicast source to the receivers, as shown in Figure 82 .
The IPv6 multicast forwarding table on Router C contains the (S, G) entry, with VLAN-interface 20 as the
RPF interface.
Figure 82 RPF check process
• When an IPv6 multicast packet arrives on VLAN-interface 20 of Router C, because the interface is
the incoming interface of the (S, G) entry, the router forwards the packet to all outgoing interfaces.
• When an IPv6 multicast packet arrives on VLAN-interface 10 of Router C, 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 Source (the RPF
interface) is VLAN-interface 20. This means that the (S, G) entry is correct and the packet arrived
along a wrong path. The RPF check fails and the packet is discarded.
Configuration task list
Complete these tasks to configure IPv6 multicast routing and forwarding:
Task Remarks
Enabling IPv6 multicast routing Required
Configuring an IPv6 multicast routing policy Optional
Configuring an IPv6 multicast forwarding range Optional
Configuring IPv6 multicast
routing and forwarding
Configuring the IPv6 multicast forwarding table size Optional