H3C Technologies H3C SecPath F1000-E - Manual (Page 15)

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Multicast Routing and Forwarding
Configuration
This chapter includes these sections:
• Multicast Routing and Forwarding Overview
• Configuration Task List
• Displaying and Maintaining Multicast Routing and Forwarding
• Configuration Examples
• Troubleshooting Multicast Routing and Forwarding
NOTE:
The term router in this document refers to network routing devices running a routing protocol.
Multicast Routing and Forwarding Overview
Introduction to Multicast Routing and Forwarding
In multicast implementations, multicast routing and forwarding are implemented by three types of tables:
• Each multicast routing protocol has its own multicast routing table, such as PIM routing table.
• The multicast routing information of different multicast routing protocols forms a general multicast
routing table.
• The multicast forwarding table is directly used to control the forwarding of multicast packets.
A multicast routing 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
multicast protocols, its multicast routing table includes routes generated by multiple protocols. The router
chooses the optimal route from the multicast routing table based on the configured multicast routing and
forwarding policy and adds the route entry into its multicast forwarding table.
RPF Check Mechanism
A multicast routing protocol relies on the existing unicast routes, MBGP routes, or multicast static routes
in creating multicast routing entries. When creating multicast routing table entries, a multicast routing
protocol uses the reverse path forwarding (RPF) check mechanism to ensure multicast data delivery along
the correct paths. In addition, the RPF check mechanism also helps avoid data loops.
RPF check process
An RPF check is based on a unicast route, MBGP route, or multicast static route.
• A unicast routing table contains the shortest path to each destination subnet,
• An MBGP routing table contains multicast routing information, and
• A multicast static routing table contains the RPF routing information defined by the user through
static configuration.