The igmp require-router-alert command configures an interface to accept only IGMP messages containing the Router-Alert option in IP headers.
The undo igmp require-router-alert command restores the default configuration.
By default, an interface accepts and processes all received IGMP messages, including the IGMP messages without the Router-Alert option.
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Usage Scenario
If a packet carries the Router-Alert option, the packet needs to be sent to the routing protocol layer for processing. The igmp require-router-alert command enables a device to accept only IGMP messages carrying the Router-Alert option, thus improving IGMP security.
Prerequisites
The multicast routing function has been enabled using the multicast routing-enable command in the public network instance view or VPN instance view.
Configuration Impact
After the igmp require-router-alert command is run on an interface, the interface checks whether a received IGMP message carries the Router-Alert option. If the IGMP message does not carry the Router-Alert option, the interface discards the IGMP message.
NOTE: The igmp require-router-alert command is valid for IGMPv2 and IGMPv3. In IGMPv1, an interface does not check whether a received IGMP message carries the Router-Alert option, even if the igmp require-router-alert command is run on the interface.Precautions
The function of the igmp require-router-alert command is the same as the function of the require-router-alert command in the IGMP view. The configuration in the IGMP view is effective for all interfaces, whereas the configuration in the interface view is effective only for the specified 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 available.