H3C Technologies H3C SecPath F1000-E - Manual (Page 156)

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2. If the corresponding (S, G) entry exists, and the interface on which the packet actually arrived is
the incoming interface, the router forwards the packet to all the outgoing interfaces.
3. If the corresponding (S, G) entry exists, but the interface on which the packet actually arrived is not
the incoming interface in the IPv6 multicast forwarding table, the IPv6 multicast packet is subject to
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 is to be discarded.
If the RPF interface is not the incoming interface, this means the (S, G) entry has expired, and router
replaces the incoming interface with the RPF interface. If the interface on which the packet arrived in 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 1 . The
IPv6 multicast forwarding table on Router C contains the (S, G) entry, with POS 5/1 as the RPF interface.
Figure 1 RPF check process
• When an IPv6 multicast packet arrives on POS 5/1 of Router C, as 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 POS 5/0 of Router C, as 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 POS
5/1. This means the (S, G) entry is correct and 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 Optional
Configuring IPv6 Multicast Configuring an IPv6 Multicast Routing Policy Optional