HPE FlexNetwork 5510 HI Series Configuration Manual page 252

packet as the incoming interface of the (S, G) entry. After the router receives another (S, G) packet, it
looks up its IPv6 multicast forwarding table for a matching (S, G) entry:
• If no match is found, the router first determines the RPF route back to the packet source. Then,
it creates a forwarding entry with the RPF interface as the incoming interface and performs one
of the following tasks:
If the receiving interface is the RPF interface, the RPF check succeeds and the router

forwards the packet out of all outgoing interfaces.
If the receiving interface is not the RPF interface, the RPF check fails and the router

discards the packet.
• If a match is found and the matching forwarding entry contains the receiving interface, the
router forwards the packet out of all outgoing interfaces.
• If a match is found but the matching forwarding entry does not contain the receiving interface,
the router determines the RPF route back to the packet source. Then, the router performs one
of the following tasks:
If the RPF interface is the incoming interface, it means that the forwarding entry is correct

but the packet traveled along a wrong path. The packet fails the RPF check, and the router
discards the packet.
If the RPF interface is not the incoming interface, it means that the forwarding entry has

expired. The router replaces the incoming interface with the RPF interface and matches the
receiving interface against the RPF interface. If the receiving interface is the RPF interface,
the router forwards the packet out of all outgoing interfaces. Otherwise, it discards the
packet.
Figure 80 RPF check process
IPv6 routing table on Device C
Destination/Prefix
2000::/16
Source
2000::101/16
IPv6 multicast packets
As shown in Figure 80, assume that IPv6 unicast routes are available on the network. IPv6 MBGP is
not configured. IPv6 multicast packets travel along the SPT from the multicast source to the
receivers. The IPv6 multicast forwarding table on Device C contains the (S, G) entry, with
VLAN-interface 20 as the RPF interface.
• If an IPv6 multicast packet arrives at Device C on VLAN-interface 20, the receiving interface is
the incoming interface of the (S, G) entry. Device C forwards the packet out of all outgoing
interfaces.
• If an IPv6 multicast packet arrives at Device C on VLAN-interface 10, the receiving interface is
not the incoming interface of the (S, G) entry. Device C searches its IPv6 unicast routing table
and finds that the outgoing interface to the source (the RPF interface) is VLAN-interface 20.
This means that the (S, G) entry is correct but the packet traveled along a wrong path. The
packet fails the RPF check, and Device C discards the packet.
Interface
Vlan-int20
Device A
Vlan-int20
242
Receiver
Device B
Vlan-int10
Receiver
Vlan-int10
Device C