igmp prompt-leave

Function

The igmp prompt-leave command enables the fast leave function on an interface. This function enables an IGMP querier to delete IGMP entries immediately after receiving Leave messages from group members, without sending Group-Specific Query messages.

The undo igmp prompt-leave command disables fast leave on an interface.

By default, an IGMP querier sends a Group-Specific Query message after receiving a Leave message for a specific multicast group.

Format

igmp prompt-leave [ group-policy acl-number ]

undo igmp prompt-leave

Parameters

Parameter	Description	Value
group-policy	Specifies an IGMP group policy. If this parameter is specified, the fast leave function takes effect only for multicast groups specified in the policy. When specifying this parameter, ensure that the referenced ACL has been configured. The device filters Leave messages on the interface based on the ACL. If a host leaves a multicast group in the range permitted by the ACL, the device immediately deletes the multicast group entry without sending a Group-Specific Query message. If a host leaves a multicast group out of the range permitted by the ACL, the device sends a Group-Specific Query message. If this parameter is not specified, the fast leave function takes effect for all multicast groups.	-
acl-number	Specifies the number of a basic ACL or an advanced ACL. This ACL defines a range of multicast groups. The specified ACL is configured using the acl command.	The number of a basic ACL is an integer that ranges from 2000 to 2999. The number of an advanced ACL ranges from 3000 to 3999.

Views

GE interface view, XGE interface view, MultiGE interface view, 25GE interface view, 40GE interface view, 100GE interface view, Eth-Trunk interface view, GE sub-interface view, XGE sub-interface view, MultiGE sub-interface view, 25GE sub-interface view, 40GE sub-interface view, 100GE sub-interface view, Eth-Trunk sub-interface view, VLANIF interface view, loopback interface view

Default Level

2: Configuration level

Usage Guidelines

Usage Scenario

In some scenarios, a querier interface connects to only one receiver host. If the host frequently switches between multiple multicast groups, you can configure the fast leave function on the interface so that the interface can quickly respond to Leave messages sent from the host. After the fast leave function is configured, the querier does not send a Group-Specific Query message after receiving a Leave message. Instead, the querier directly notifies the upstream multicast device that the host has left the multicast group. The fast leave function reduces delay in response to Leave messages and saves network bandwidth.

Prerequisites

IP multicast routing has been enabled using the multicast routing-enable command.

Precautions

IGMP fast leave applies only to IGMPv2 and IGMPv3.
When an interface has more than one receiver connected, enabling the fast leave function interrupts multicast traffic of the other receivers in the multicast group. It is recommended that you enable this function only on interfaces with one receiver.
This command functions in the same way as the prompt-leave command used in the IGMP view, except that the configuration in the IGMP view is globally valid, whereas the configuration in the interface view is valid only for the specific interface. The configuration in the interface view takes precedence over the configuration in the IGMP view. The configuration in the IGMP view is used only when the configuration in the interface view is not done.

Example

# Create ACL 2005 and configure a rule that allows hosts to fast leave multicast groups in the range of 225.1.0.0/16. Configure fast leave on VLANIF100.

<HUAWEI> system-view
[HUAWEI] acl number 2005
[HUAWEI-acl-basic-2005] rule permit source 225.1.0.0 0.0.255.255
[HUAWEI-acl-basic-2005] quit
[HUAWEI] multicast routing-enable
[HUAWEI] interface vlanif 100
[HUAWEI-Vlanif100] igmp prompt-leave group-policy 2005

# Create ACL 2005 and configure a rule that allows hosts to fast leave multicast groups in the range of 225.1.0.0/16. Configure fast leave on GE0/0/1.

<HUAWEI> system-view
[HUAWEI] acl number 2005
[HUAWEI-acl-basic-2005] rule permit source 225.1.0.0 0.0.255.255
[HUAWEI-acl-basic-2005] quit
[HUAWEI] multicast routing-enable
[HUAWEI] interface gigabitethernet 0/0/1
[HUAWEI-GigabitEthernet0/0/1] undo portswitch
[HUAWEI-GigabitEthernet0/0/1] igmp prompt-leave group-policy 2005