The require-router-alert command configures the switch to discard MLD messages without the Router-Alert option.
The undo require-router-alert command disables the switch from checking the Router-Alert option in MLD messages.
By default, the switch does not check whether the received MLD messages contain Router-Alert options in IPv6 headers, and it accepts all the received MLD messages.
Usage Scenario
Generally, a network device sends a message to the routing protocol module for processing only when the destination address of the message is a local interface address. Destination addresses of MLD messages are multicast addresses but not addresses of interfaces on multicast devices. Therefore, multicast devices do not send MLD messages to the MLD module for processing, and the MLD module cannot maintain group memberships.
The Router-Alert option in the IPv6 header of an MLD message solves this problem. If an MLD message contains the Router-Alert option, the device sends the message to the MLD module.
You can configure the device to accept only MLD messages with the Router-Alert option to improve MLD security.
Prerequisites
Layer 3 IPv6 multicast has been enabled using the multicast ipv6 routing-enable command in the system view.
Precautions
The function of this command is the same as that of the mld require-router-alert command used in the interface view. The configuration in the MLD view is globally valid, whereas the configuration in the interface view takes effect only for the specified interface. The configuration in the interface view takes precedence over the configuration in the MLD view. The configuration in the MLD view is used only when no configuration is performed in the interface view.