H3C Technologies H3C S10500 Series Switches - Manual (Page 333)

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IPv6 multicast routing and forwarding
configuration
NOTE:
•
The term router in this document refers to both routers and Layer 3 switches.
• The term interface in the IPv6 multicast routing and forwarding features refers to Layer 3 interfaces,
including VLAN interfaces and route-mode (or Layer 3) Ethernet ports. You can set an Ethernet port to
operate in route mode by using the port link-mode route command (see Layer 2—LAN Switching
Configuration Guide).
IPv6 multicast routing and forwarding overview
In IPv6 multicast implementations, the following types of tables implement multicast routing and
forwarding:
• Multicast routing table of an IPv6 multicast routing protocol—Each IPv6 multicast routing protocol
has its own multicast routing table, such as IPv6 PIM routing table.
• General IPv6 multicast routing table—The multicast routing information of different IPv6 multicast
routing protocols forms a general IPv6 multicast routing table.
• IPv6 multicast forwarding table—The IPv6 multicast forwarding table guides the forwarding of IPv6
multicast packets.
An IPv6 multicast forwarding table consists of a set of (S, G) entries. Each entry indicates the routing
information for delivering multicast data from a multicast source to a multicast group. If a router supports
multiple IPv6 multicast protocols, its IPv6 multicast routing table will include routes that these protocols
have generated. The router chooses the optimal route from the IPv6 multicast routing table based on the
configured multicast routing and forwarding policy and installs the route entry into its IPv6 multicast
forwarding table.
RPF check mechanism
An IPv6 multicast routing protocol relies on the existing IPv6 unicast routing information or IPv6 MBGP
routes in creating IPv6 multicast routing entries. When creating IPv6 multicast routing table entries, an
IPv6 multicast routing protocol uses the reverse path forwarding (RPF) check mechanism to ensure IPv6
multicast data delivery along the correct path. The RPF check mechanism also helps avoid data loops
caused by various reasons.
RPF check process
An RPF check is based on one of the following routing tables:
• IPv6 unicast routing table—Contains the shortest path to each destination subnet
• IPv6 MBGP routing table—Contains IPv6 multicast routing information
When a router performs an RPF check, it searches its IPv6 unicast routing table and IPv6 MBGP routing
table at the same time. The specific process is as follows: