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Configuration Guide - IP Multicast

CloudEngine 12800 and 12800E V200R005C10

This document describes the configurations of IP multicast, including IP multicast basics, IGMP, MLD, PIM (IPv4), PIM (IPv6), MSDP, multicast VPN, multicast route management (IPv4), multicast route management (IPv6), IGMP snooping, MLD snooping, static multicast MAC address, multicast VLAN, multicast network management.
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Multicast Routing and Forwarding

Multicast Routing and Forwarding

Devices performing different roles on a multicast network maintain different multicast tables, including the Internet Group Management Protocol (IGMP) group table, multicast protocol routing table, multicast routing table, and multicast forwarding information base (MFIB). The following sections describe the functions of these tables in multicast route management.

IGMP Group

A multicast router creates an IGMP group entry when it receives an IGMP Join message from a host. The router maintains group memberships in IGMP group entries and instructs a multicast routing protocol, usually the Protocol Independent Multicast (PIM) protocol, to create corresponding (*, G) entries. The router maintains an IGMP group entry for each interface provided that the interfaces have IGMP enabled and have received IGMP Join messages.

The following is an example of a group entry on an interface:

<HUAWEI> display igmp group
Interface group report information of VPN instance: public net
 Vlanif100(10.1.6.2):
  Total 1 IGMP Group reported
   Group Address   Last Reporter   Uptime      Expires
   225.1.1.2       10.1.6.10       00:02:04    00:01:17

Table 8-2 explains the fields of this IGMP group entry.

Table 8-2 Description of fields in the IGMP group entry
Field Description
Group Address Indicates the address of the group that an interface has joined.
Last Reporter Indicates the IP address of the last user that sent an IGMP Join message to the group.
Uptime Indicates the time elapsed since the group was created.
Expires Indicates the time remaining before the group will be aged out.

Multicast Protocol Routing Table

Multicast routing protocols maintain their own routing tables to guide multicast route management. PIM is the most widely used multicast routing protocol. The following is an example of a PIM routing table:

<HUAWEI> display pim routing-table
 VPN-Instance: public net
 Total 0 (*, G) entry; 1 (S, G) entry

 (192.168.0.12, 227.0.0.1)
     RP: 10.2.2.2
     Protocol: pim-sm, Flag: SPT LOC ACT
     UpTime: 02:54:43
     Upstream interface: Vlanif 10
         Upstream neighbor: NULL
         RPF prime neighbor: NULL
     Downstream interface(s) information:
     Total number of downstreams: 1
         1: Vlanif 20
             Protocol: pim-sm, UpTime: 02:54:43, Expires: 00:02:47

Table 8-3 explains the fields in this PIM routing entry.

Table 8-3 Description of fields in the PIM routing entry
Field Description
(192.168.0.12, 227.0.0.1) (S, G) entry, where 192.168.0.12 is the source address and 227.0.0.1 is the group address.
RP: 10.2.2.2 Indicates the rendezvous point (RP) IP address.
Protocol: pim-sm The first Protocol field in an entry indicates the protocol that generates the entry, and the second Protocol field indicates the protocol that generates the downstream interfaces.
Flag: SPT LOC ACT Indicates the flag of the PIM routing entry.
UpTime: 02:54:43 The first UpTime field in an entry indicates how long the entry has existed, and the second UpTime field indicates how long a downstream interface has existed.
Upstream interface: Vlanif 10 Indicates the upstream interface pointing to the multicast source.
Upstream neighbor: NULL NULL indicates that no upstream neighbor is available.
RPF prime neighbor: NULL NULL indicates that no reverse path check (RPF) neighbor is available.
Downstream interface(s) information: Indicates information about downstream interfaces toward receivers.
Total number of downstreams: 1 Indicates the number of downstream interfaces.
Expires: 00:02:47 Indicates the aging time of a downstream interface.

For details about PIM routing entries, see Concepts in the PIM feature description.

Multicast Routing Table

A multicast routing table is generated and maintained by the multicast route management module of a router. If a router supports multiple multicast protocols, its multicast routing table contains the optimal routes selected from the routing tables of these protocols.

In unicast routing, routing tables of various routing protocols, such as Open Shortest Path First (OSPF), Routing Information Protocol (RIP), and Border Gateway Protocol (BGP), constitute an IP routing table. Similarly, routing tables of different multicast protocols constitute a multicast table. Routers deliver multicast routing entries to their MFIBs to guide multicast data forwarding. The following is an example of a multicast routing table:

<HUAWEI> display multicast routing-table
Multicast routing table of VPN instance: public net
 Total 0 (*, G) entry; 1 (S, G) entry

 00001: (192.168.0.2, 227.0.0.1)
       Uptime: 00:00:28
       Upstream Interface: Vlanif10
       List of 2 downstream interfaces
           1:  Vlanif20
           2:  Vlanif30

Table 8-4 explains the fields in this multicast routing entry.

Table 8-4 Description of fields in the multicast routing entry
Field Description
00001: (192.168.0.2, 227.0.0.1) 00001 is the entry number, and (FC00::2, FFE3::1) is an (S, G) entry, where S indicates a source address and G indicates a group address.
Uptime: 00:00:28 Indicates the time elapsed since the multicast routing entry was updated.
Upstream Interface: VlanifIndicates the 10 Indicates the upstream interface pointing to the multicast source.
List of 2 downstream interfaces Indicates the downstream interfaces toward receivers.

MFIB

An MFIB is created and maintained by the route management module of a router according to multicast routing information. Routers forward multicast data according to their MFIBs. You can use the display multicast ip fib command to view entries in an MFIB. An MFIB has the same functions as a unicast FIB. The following is an example of an MFIB.

<HUAWEI> display multicast ip fib
Multicast Forwarding Table of VPN-Instance: public net 
Total 1 entry, 1 matched 

1.(10.10.10.2, 225.0.0.1) 
     Index : 10 
     Flags : 1 
     Timeout: 00:03:26 
     Incoming interface : Vlanif10 
     Outgoing Interfaces: 2 
       1: Vlanif20 
       1: Vlanif30 
     Matched packets :34640 packets(3602664 bytes) 
     Wrong interface :0 packets
     Forwarded       :34640 packets(3602664 bytes)

Table 8-5 explains the fields in this multicast forwarding entry.

Table 8-5 Description of fields in the multicast forwarding entry
Field Description

1. (10.10.10.2, 225.0.0.1)

1 is the entry number, and (10.10.10.2, 225.0.0.1) is an (S, G) entry, where S indicates a source address and G indicates a group address.

Index : 10

Indicates the unique identifier of the multicast forwarding entry in the MFIB. It is used to rapidly search the MFIB.

Flags : 1

Indicates the flag of the multicast forwarding entry.
Timeout: 00:03:26 Indicates how soon the multicast forwarding entry will time out.
Incoming interface: Vlanif10 Indicates the inbound interface in the multicast forwarding entry.
Outgoing Interfaces: 2 Lists the outbound interfaces toward receivers.
Matched packets :34640 packets(3602664 bytes) Indicates the number of packets of packets that match the multicast forwarding entry.
Wrong interface :0 packets Indicates the number of packets that arrive on the incorrect inbound interfaces.
Forwarded :34640 packets(3602664 bytes) Indicates the number of forwarded packets.

The preceding information shows that multicast data is forwarded according to the MFIB. Each multicast forwarding entry records statistics about packets that are forwarded according to the entry.

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Updated: 2019-04-20

Document ID: EDOC1100074724

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