HP VPN Firewall Appliances Appendix Protocol Reference

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NOTE:
Some device models allow you to configure special processing of IPv6 multicast packets that have failed
an RPF check instead of simply dropping them.
As shown in Figure 65, 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. The
IPv6 multicast forwarding table on Router C contains the (S, G) entry, with POS 5/1 as the RPF interface.
Figure 65 RPF check process
• When POS 5/1 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 to all outgoing interfaces.
• When POS 5/0 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 Source (the RPF
interface) is POS 5/1. 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.
IPv6 multicast forwarding across IPv6 unicast
subnets
Routers forward the IPv6 multicast data from an IPv6 multicast source hop by hop along the forwarding
tree, but some routers might not support IPv6 multicast protocols in a network. When the IPv6 multicast
data is forwarded to a router that does not support IPv6 multicast, the forwarding path is blocked. In this
case, you can enable IPv6 multicast data forwarding across the IPv6 unicast subnets by establishing a
generic routing encapsulation (GRE) tunnel between the routers at both ends of the IPv6 unicast subnets.
For more information about GRE, see VPN Configuration Guide.
Receiver
Receiver
Source
2000::101/16
Router A
Router B
Router C
POS5/1
POS5/0
POS5/0
IPv6 Multicast packets
Destination/Prefix
IPv6 Routing Table on Router C
2000::/16
Interface
POS5/1