Configuring Ipv6 Multicast Routing And Forwarding; Overview; Rpf Check Mechanism - HP 6125G Configuration Manual

Configuring 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
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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
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routing protocols forms a general IPv6 multicast routing table.
IPv6 multicast forwarding table—The IPv6 multicast forwarding table guides the forwarding of IPv6
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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.
The term "router" in this document refers to both routers and Layer 3 switches.

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.
An RPF check is based on one of the following routing tables:
IPv6 unicast routing table—Contains the shortest path to each destination subnet
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IPv6 MBGP routing table—Contains IPv6 multicast routing information
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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:
The router chooses each optimal route from the IPv6 unicast routing table and the IPv6 MBGP
1.
routing table:
The router searches its IPv6 unicast routing table by using the IPv6 address of the packet source
as the destination address and automatically selects the optimal route as the RPF route. 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 IPv6 multicast packet from the
RPF neighbor arrived on the RPF interface to be the shortest path that leads back to the source.
The router automatically chooses an optimal IPv6 MBGP route by searching its MBGP routing
table, and using the IPv6 address of the packet source as the destination address. The outgoing
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