igmp-snooping prompt-leave

Function

The igmp-snooping prompt-leave command enables member ports to promptly leave related multicast groups.

The undo igmp-snooping prompt-leave command restores the default configuration.

By default, a member port is not allowed to promptly leave a multicast group.

Format

igmp-snooping prompt-leave [ group-policy { acl-number | acl-name acl-name } ]

undo igmp-snooping prompt-leave

Parameters

Parameter	Description	Value
group-policy	Specifies a multicast group policy for prompt leave. The policy specifies the multicast groups that member ports can promptly leave.	-
acl-number	Specifies the number of a basic ACL.	The value is an integer ranging from 2000 to 3999.
acl-name acl-name	Specifies the name of a named ACL.	The value is a string of 1 to 64 case-sensitive characters, spaces not supported. The name must start with a letter or digit, and cannot contain only digits.

Parameter

Description

Value

group-policy

Specifies a multicast group policy for prompt leave. The policy specifies the multicast groups that member ports can promptly leave.

acl-number

Specifies the number of a basic ACL.

The value is an integer ranging from 2000 to 3999.

acl-name acl-name

Specifies the name of a named ACL.

The value is a string of 1 to 64 case-sensitive characters, spaces not supported. The name must start with a letter or digit, and cannot contain only digits.

Views

VLAN view

Default Level

2: Configuration level

Task Name and Operations

Task Name	Operations
l2mc	write

Usage Guidelines

Usage Scenario

After receiving an IGMP Leave message for a multicast group from a host, a device enabled with prompt leave directly deletes the forwarding entry of the multicast group, without sending group-specific query messages. When an interface is connected to only one host, the prompt leave mechanism can be used to shorten the response delay and release bandwidth resources in a timely manner.

If group-policy or group-policy acl-name is not set in the igmp-snooping prompt-leave command, prompt leave will take effect for all multicast groups.

If group-policy or group-policy acl-name is set in this command, the configured ACL will be used to filter Leave messages received in the VLAN.

When a member port of a device receives a Leave message and the group address of the Leave message is within the range allowed by the ACL, the device will immediately delete the member port and notify the upstream device of the Leave event.
When a member port of a device receives a Leave message and the group address of the Leave message is beyond the range allowed by the ACL, the device will send a group-specific query message.

Prerequisites

IGMP snooping is enabled globally and in a VLAN.

Rules have been configured for a specified basic ACL. By default, the ACL rule in which the action is permit is applicable to all multicast groups. To enable prompt leave for a multicast group, you also need to run the rule (basic ACL view) deny source any or rule (advanced ACL view) deny source any command.

Configuration Impact

Running the igmp-snooping prompt-leave command on an interface connected to multiple user hosts is not recommended. If this command is run on the interface, the leave of one user host will cause other use hosts in the group to fail to receive multicast data.If the igmp-snooping prompt-leave command is run several times, the latest configuration overrides the previous one.

Precautions

This command fails to be run in a VLAN when a Dot1q termination sub-interface has been added to the VLAN.

Example

# Allow member ports in VLAN 2 to promptly leave multicast group 225.1.1.123.

<HUAWEI> system-view
[~HUAWEI] acl number 2008
[*HUAWEI-acl-basic-2008] rule permit source 225.1.1.123 0
[*HUAWEI-acl-basic-2008] quit
[*HUAWEI] igmp-snooping enable
[*HUAWEI] vlan 2
[*HUAWEI-vlan2] igmp-snooping prompt-leave group-policy 2008