Configuring Ipv6 Multicast Routing And Forwarding - HP A8800 Configuration Manual

Configuring IPv6 multicast routing and
forwarding
Overview
In IPv6 multicast implementations, multicast routing and forwarding are implemented by the following
types of tables:
• Multicast routing table of an IPv6 multicast routing protocol—Each IPv6 multicast routing protocol
has its own multicast routing table, such as the 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 indicating 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 generated by these
protocols. 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) to ensure IPv6 multicast data
delivery along the correct path. In addition, the RPF check mechanism also helps avoid data loops
caused by various reasons.
The basis for an RPF check is an IPv6 unicast route or an IPv6 MBGP route:
IPv6 unicast routing table—Contains unicast routing information.
•
IPv6 MBGP routing table—Contains IPv6 MBGP multicast routing information.
•
RPF check process
When performing an RPF check, a router searches its IPv6 unicast routing table and IPv6 MBGP routing
table at the same time. The specific process is as follows:
1. The router first chooses an optimal route from the IPv6 unicast routing table and the IPv6 MBGP
routing table:
The router automatically chooses an optimal unicast route by searching its IPv6 unicast routing
table, using the IPv6 address of the "packet source" as the destination address. The outgoing
interface in the corresponding routing entry is the RPF interface and the next hop is the RPF
neighbor. The router considers the path along which the packet from the RPF neighbor arrived
on the RPF interface to be the shortest path that leads back to the source.
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