igmp-snooping require-router-alert

Function

The igmp-snooping require-router-alert command configures a device to accept IGMP messages that contain the Router-Alert option in the IP header from a VLAN.

The undo igmp-snooping require-router-alert command restores the default setting.

By default, the IGMP messages accepted by a device from a VLAN do not need to carry the Router Alert option.

Format

igmp-snooping require-router-alert

undo igmp-snooping require-router-alert

Parameters

None

Views

VLAN view

Default Level

2: Configuration level

Task Name and Operations

Task Name	Operations
l2mc	write

Usage Guidelines

Usage Scenario

Router-Alert is a mechanism used to identify protocol packets. Packets carrying Router-Alert options are delivered to the routing protocol layer for processing.

By default, devices do not check whether packets carry Router-Alert options for the sake of compatibility, and send all IGMP messages to the upper layer for processing. To improve device performance, reduce costs, and ensure protocol security, the igmp-snooping require-router-alert command can be used to configure a device to discard IGMP messages that do not carry the Router-Alert option. After receiving IGMP messages, this device will check whether these messages carry the Router-Alert option. If the messages do not carry the Router-Alert option, this device will discard them.

Precautions

The igmp-snooping require-router-alert command fails to be run in the VLAN view when a Dot1q termination sub-interface has been added to the VLAN.

Example

# Configure a device in VLAN 2 to accept only IGMP messages that carry the Router-Alert option in the IP header.

<HUAWEI> system-view
[~HUAWEI] igmp-snooping enable
[*HUAWEI] vlan 2
[*HUAWEI-vlan2] igmp-snooping enable
[*HUAWEI-vlan2] igmp-snooping require-router-alert