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Configuration Guide - IP Multicast

S7700 and S9700 V200R010C00

This document describes IP multicast basics and how to configure IP multicast features, including IGMP/MLD, PIM (IPv4&IPv6), MSDP, multicast VPN, Layer 3 multicast CAC, Layer 2 multicast CAC, IGMP/MLD snooping, and multicast VLAN, IPv4&IPv6 multicast route management, static multicast MAC address, multicast network.
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Configuring IGMP Limit

Configuring IGMP Limit

Pre-configuration Tasks

Configuring Basic IGMP Functions


As defined in multicast protocols, group members can join or leave a group anytime, anywhere, and the number of members in a group is unlimited. If too many users stream videos at the same time, a large amount of bandwidth is consumed, degrading the forwarding performance of the multicast device. The IGMP limit function solves this problem by restricting the number of multicast groups allowed in the system, in a virtual private network (VPN) instance, and on an interface. This allows users who have joined multicast groups to stream high-quality videos. When the switch receives an IGMP Report message and needs to create a new IGMP entry, it checks whether the number of IGMP entries exceeds the limit. If not, the switch creates the IGMP entry and forwards multicast data to the multicast group.

The global IGMP limit restricts the number of entries on all interfaces. The IGMP limit configured in a VPN instance restricts the number of IGMP entries in the VPN instance. The IGMP limit configured on an interface restricts the number of IGMP entries on the interface.

The switch counts IGMP entries as follows:
  • Counts each (*, G) entry as one entry.
  • Counts each (S, G) entry as one entry.
  • Counts each (*, G) entry established with IGMP SSM mapping as one entry but does not count (S, G) entries converted from (*, G) entries.

To apply global, VPN-based, and interface-based IGMP limits together on a switch, you are advised to set the IGMP limit values following this rule: global IGMP limit value > IGMP limit value in a VPN instance > IGMP limit value on an interface.


  • Configuring the global IGMP limit
    1. Run:


      The system view is displayed.

    2. Run:

      igmp global limit number

      The maximum number of IGMP entries allowed in the system is configured.

  • Configuring the IGMP limit in a VPN instance
    1. Run:


      The system view is displayed.

    2. Run:

      igmp [ vpn-instance vpn-instance-name ]

      The IGMP view of a public or VPN instance is displayed.

    3. Run:

      limit number

      The maximum number of IGMP entries allowed in the public or VPN instance is configured.

  • Configuring the IGMP limit on an interface
    1. Run:


      The system view is displayed.

    2. Run:

      interface interface-type interface-number

      The interface view is displayed.

    3. (Optional) On an Ethernet interface, run undo portswitch

      The interface is switched to Layer 3 mode.

      By default, an Ethernet interface works in Layer 2 mode.

    4. Run:

      igmp limit number [ except { acl-number | acl-name acl-name } ]

      The maximum number of IGMP entries allowed on the interface is configured.

      If except is not specified in the command, the configured limit value limits the number of dynamic (*, G) and (S, G) entries.

      Before specifying except, configure the associated ACL. The interface then filters the received IGMP Report messages according to the ACL. The IGMP limit does not apply to the entries allowed by the ACL.

Checking the Configuration

  • Run the display igmp [ vpn-instance vpn-instance-name | all-instance ] interface [ interface-type interface-number | up | down ] [ verbose ] command to check the IGMP configuration and running status on an interface.

Updated: 2019-08-21

Document ID: EDOC1000141903

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