Configuring Ipv6 Multicast Routing And Forwarding; Overview; Rpf Check Mechanism - HP MSR2003 Configuration Manual

Configuring IPv6 multicast routing and
forwarding
In this chapter, "MSR2000" refers to MSR2003. "MSR3000" collectively refers to MSR3012, MSR3024,
MSR3044, MSR3064. "MSR4000" collectively refers to MSR4060 and MSR4080.

Overview

IPv6 multicast routing and forwarding uses the following tables:
IPv6 multicast protocols' routing tables, such as the IPv6 PIM routing table.
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• General IPv6 multicast routing table that summarizes the multicast routing information generated by
different IPv6 multicast routing protocols. The IPv6 multicast routing information from IPv6 multicast
sources to IPv6 multicast groups are stored in a set of (S, G) routing entries.
IPv6 multicast forwarding table that guides IPv6 multicast forwarding. The optimal routing entries in
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the IPv6 multicast routing table are added to the 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.
A multicast routing protocol uses the following tables to perform the RPF check:
IPv6 unicast routing table—Contains unicast routing information.
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IPv6 MBGP routing table—Contains IPv6 MBGP multicast routing information.
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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 using the following process:
1. The router separately chooses an optimal route from the IPv6 unicast routing table and the IPv6
MBGP routing table.
The router searches its IPv6 unicast routing table for an optimal route back to the packet source.
The outgoing interface of the route is the RPF interface and the next hop is the RPF neighbor. The
router considers the path of the IPv6 multicast packet that the RPF interface receives from the RPF
neighbor as the shortest path that leads back to the source.
The router searches its IPv6 MBGP routing table for an optimal MBGP route back to the packet
source. The outgoing interface of the route is the RPF interface and the next hop is the RPF
neighbor.
2. The router selects one of the optimal routes as the RPF route according to the following principles:
If the router uses the longest prefix match principle, the router selects the matching route as the
RPF route. If the routes have the same prefix length, the router selects the route that has a higher
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