F3726, F3211, F3174, R5135, R3816-HP Firewalls and UTM Devices Appendix Protocol Reference-6PW100

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.

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 65.

he 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

Source

2000::101/16

Router A

Router B

Router C

POS5/1

POS5/0

IPv6 Multicast packets

Destination/Prefix

IPv6 Routing Table on Router C

2000::/16

Interface

POS5/1