Configuring IGMP Limit

Pre-configuration Tasks

Context

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 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 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.

Procedure

Configuring the global IGMP limit
1. Run system-view
  The system view is displayed.
2. Run igmp global limit number
  The maximum number of IGMP entries allowed in the system is configured.
  
  You can also run the limit number command in the IGMP view to set the global IGMP limit. If both the igmp global limit and limit number commands are executed, the smaller value takes effect.
Configuring the IGMP limit on an interface
1. Run system-view
  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.
  
  Only the S5720-EI, S5720-HI, S5730-HI, S5731-H, S5731-S, S5731S-H, S5731S-S, S5732-H, S6720-EI, S6720-HI, S6720S-EI, S6730-H, S6730S-H, S6730-S, and S6730S-S support switching between Layer 2 and Layer 3 modes.
4. Run igmp limit number [ except acl-number ]
  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.

Verifying the Configuration

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