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

Configuring 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

The following tables are involved in multicast routing and forwarding:
Multicast routing table of each multicast routing protocol, such as the PIM routing table.
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• General multicast routing table that summarizes multicast routing information generated by different
multicast routing protocols. The multicast routing information from multicast sources to multicast
groups are stored in a set of (S, G) routing entries.
Multicast forwarding table that guides multicast forwarding. The optimal routing entries in the
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multicast routing table are added to the multicast forwarding table.

RPF check mechanism

A multicast routing protocol relies on the existing unicast routes, MBGP routes, or static multicast routes
to create multicast routing entries. When creating multicast routing entries, the multicast routing protocol
uses reverse path forwarding (RPF) check to ensure the multicast data delivery along the correct path. The
RPF check also helps avoid data loops.
A multicast routing protocol uses the following tables to perform an RPF check:
Unicast routing table—Contains unicast routing information.
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MBGP multicast routing table—Contains MBGP multicast routing information.
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• Static multicast routing table—Contains RPF routes that are manually configured.
MBGP multicast routing table and static multicast routing table are used for RPF check rather than
multicast routing.
RPF check process
When performing an RPF check, the router searches its unicast routing table, MBGP routing table, and
static multicast routing table at the same time using the following process:
1. The router separately chooses an optimal route from the unicast routing table, MBGP routing table,
and the static multicast routing table:
The router looks up its unicast routing table for an optimal unicast 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 packet that the RPF interface receives from the RPF
neighbor as the shortest path that leads back to the source.
The router looks up its 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.
The router looks up its static multicast routing table for an optimal static multicast route back to
the packet route. The route explicitly defines the RPF interface and the RPF neighbor.
2. The router selects one of the three optimal routes as the RPF route according to the following
principles:
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