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CLI-based Configuration Guide - IP Multicast

AR500, AR510, and AR530 V200R007

This document describes the principles and configurations of IP multicast, and provides configuration examples.
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Huawei uses machine translation combined with human proofreading to translate this document to different languages in order to help you better understand the content of this document. Note: Even the most advanced machine translation cannot match the quality of professional translators. Huawei shall not bear any responsibility for translation accuracy and it is recommended that you refer to the English document (a link for which has been provided).
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, IGMP routing 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 and Routing Tables

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
 GigabitEthernet0/0/1(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.

IGMP also maintains an IGMP routing table. An interface is included in an IGMP routing entry only when PIM is not enabled on the interface. The IGMP routing table increases the number of available outbound interfaces for multicast routing entries. The following is an example of an IGMP routing entry:

<Huawei> display igmp routing-table
Routing table of VPN-Instance: public net
 Total 1 entries

 00001. (*, 225.1.1.1)
       List of 1 downstream interface
        GigabitEthernet0/0/1 (10.20.20.1)
                   Protocol: IGMP

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

Table 8-3  Description of fields in the IGMP routing entry
Field Description
00001. (*, 225.1.1.1) 00001 is the entry number, and (*, 225.1.1.1) is an (*, G) entry, where * indicates any source and G indicates a group address.
List of 1 downstream interface Indicates the downstream interfaces toward receivers.
Protocol: IGMP Indicates the protocol that generates the downstream interfaces.

According to the command output, the downstream interface is generated by IGMP, indicating that PIM is not enabled on the interface. If PIM is enabled on an interface, the routing entries of the interface are maintained by PIM.

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: GigabitEthernet1/0/0
         Upstream neighbor: NULL
         RPF prime neighbor: NULL
     Downstream interface(s) information:
     Total number of downstreams: 1
         1: GigabitEthernet2/0/0
             Protocol: pim-sm, UpTime: 02:54:43, Expires: 00:02:47

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

Table 8-4  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, which is displayed only when the protocol type is PIM-SM.
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: GigabitEthernet1/0/0 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 1 entry
 00001. (192.168.0.2, 227.0.0.1)
       Uptime: 00:00:28
       Upstream Interface: GigabitEthernet1/0/0
       List of 2 downstream interfaces
           1:  GigabitEthernet2/0/0
           2:  GigabitEthernet3/0/0

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

Table 8-5  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: GigabitEthernetIndicates the 1/0/0 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 forwarding-table 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 forwarding-table
Multicast Forwarding Table of VPN-Instance: public net
Total 1 entry, 1 matched

00001. (10.10.10.2, 225.0.0.1)
     MID: 10, Flags: ACT
     Uptime: 00:08:32, Timeout in: 00:03:26
     Incoming interface: GigabitEthernet1/0/0
     List of 1 outgoing interfaces:
       1:  GigabitEthernet2/0/0
           Activetime: 00:23:15
     Matched 38264 packets(1071392 bytes), Wrong If 0 packets
     Forwarded 38264 packets(1071392 bytes)

Table 8-6 explains the fields in this multicast forwarding entry.

Table 8-6  Description of fields in the multicast forwarding entry
Field Description

00001. (10.10.10.2, 225.0.0.1)

00001 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.

MID: 10

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

Flags: ACT

Indicates the flag of the multicast forwarding entry.
Uptime: 00:08:32 Indicates how long the multicast forwarding entry has existed.
Timeout in: 00:03:26 Indicates how soon the multicast forwarding entry will time out.
Incoming interface: GigabitEthernet1/0/0 Indicates the inbound interface in the multicast forwarding entry.
List of 1 outgoing interfaces: Lists the outbound interfaces toward receivers.
Activetime: 00:23:15 Indicates how long an outbound interface has existed.
Matched 38264 packets(1071392 bytes) Indicates the number of packets of packets that match the multicast forwarding entry.
Wrong If 0 packets Indicates the number of packets that arrive on the incorrect inbound interfaces.
Forwarded 38264 packets(1071392 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: 2019-06-12

Document ID: EDOC1000097280

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