igmp require-router-alert

Function

The igmp require-router-alert command configures the IP header of an IGMP packet to contain the Router-Alert option on an interface.

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

By default, the interface does not check the Router-Alert option carried in IGMP packets. That is, FWs process all the received IGMP packets, including the IGMP packets without Router-Alert option.

Format

igmp require-router-alert

undo igmp require-router-alert

Parameters

None

Views

Interface view

Default Level

2: Configuration level

Usage Guidelines

After the igmp require-router-alert command is used, the interface checks the Router-Alert option carried in the IP header of a received IGMP packet. If the IP header of the received IGMP packet does not contain the Router-Alert option, the interface discards the IGMP packet.

In IGMPv1, event though the command is configured on the interface, the interface does not check whether an IGMP message carries the Router-Alert option.

The function of this command is the same as that of the require-router-alert command used in the IGMP view, except for the function range. The configuration in the IGMP view is globally valid in the instance, whereas the configuration in the interface view is valid only for the current interface. The system prefers the configuration in the system view. The configuration in the IGMP view is used only when the configuration in the interface view is not done.

You must run the multicast routing-enable command to enable the multicast function before using the command.

Example

# Configure GigabitEthernet 0/0/1 to discard the IGMP packet that does not contain the Router-Alert option.

<sysname> system-view
[sysname] multicast routing-enable
[sysname] interface GigabitEthernet 0/0/1
[sysname-GigabitEthernet0/0/1] igmp require-router-alert