Configuring IGMP Prompt-Leave

Usage Scenario

By default, IGMP-enabled interfaces send last-member query messages after receiving Leave messages for a specific multicast group from hosts. If the IGMP prompt leave function is enabled, the interfaces directly delete the records of the multicast group without sending last-member query messages. This feature shortens the delay in responding to Leave requests and reduces network bandwidth consumption. Currently, prompt-leave is available only in IGMPv2.

Pre-configuration Tasks

Before configuring prompt-leave, complete the following tasks:

Configure a unicast routing protocol to ensure that unicast routes are reachable.
Configure basic IGMP functions.

Procedure

Run system-view
The system view is displayed.
Configure a basic or an advanced ACL as needed.
If a basic ACL is used, run the rule command and set the source parameter to a multicast group address.

If an advanced ACL is used, run the rule command and set the destination parameter to a multicast group address.
- Configure a basic ACL.
  1. Run acl [ number ] basic-acl-number [ match-order { auto | config } ]
    A basic ACL is created, and the basic ACL view is displayed.
  2. Run rule [ rule-id ] [ name rule-name ] { deny | permit } source { source-ip-address { source-wildcard | 0 } | any }
    Rules are configured for the basic ACL.
- Configure an advanced ACL.
  1. Run acl { name advance-acl-name [ advance | [ advance ] number advance-acl-number ] | [ number ] advance-acl-number } [ match-order { config | auto } ]
    
    An advanced ACL is created, and the advanced ACL view is displayed.
  2. Run rule [ rule-id ] [ name rule-name ] { deny | permit } ip [ destination { destination-ip-address { destination-wildcard | 0 } | any } | source { source-ip-address { source-wildcard | 0 } | any } ] ^*
    
    Rules are configured for the advanced ACL.
Run quit
Return to the system view.
Run interface interface-type interface-number
The interface view is displayed.
Run igmp prompt-leave [ group-policy { acl-number | acl-name acl-name } ]
The IGMP prompt leave function is configured on the interface.

In an ADSL dial-up access, the IGMP querier corresponds to only one host because one host corresponds to one port. When a receiver frequently joins or leaves multiple multicast groups, enable the prompt leave function on the querier.
- If group-policy is not specified, the interface implements prompt-leave for all Leave requests.
- If group-policy is specified and a multicast group matches the permit action, the interface implements prompt-leave for Leave requests of this group.
- If group-policy is specified and a multicast group matches the deny action, the interface does not implement prompt-leave for Leave requests of this group.
- If group-policy is specified and a multicast group does not match any ACL rule, the interface does not implement prompt-leave for Leave requests of this group.
- If the ACL specified in group-policy does not exist or no rules are configured in the ACL, the interface does not implement prompt-leave for any Leave requests.
Run commit
The configuration is committed.

Checking the Configurations

# Run the display igmp [ vpn-instance vpn-instance-name | all-instance ] interface [ interface-type interface-number | up | down ] [ verbose ] command to check the configurations and operating status of IGMP on an interface.

# Run the display igmp interface verbose command to view detailed IGMP configurations of interfaces.