H3C Technologies H3C S7500E Series Switches - Manual (Page 335)

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Configuration Prerequisites
Before adjusting MLD performance, complete the following tasks:
z Configure any IPv6 unicast routing protocol so that all devices in the domain can be interoperable
at the network layer.
z Configure basic functions of MLD.
In addition, prepare the following data:
z Startup query interval
z Startup query count
z MLD query interval
z MLD querier robustness variable
z Maximum response delay of MLD general query messages
z MLD last listener query interval
z MLD other querier present interval
Configuring MLD Message Options
MLD queries include multicast-address-specific queries and multicast-address-and-source-specific
queries, and IPv6 multicast groups change dynamically, so a device cannot maintain the information
for all IPv6 multicast sources and groups. Therefore, a router may receive IPv6 multicast packets
addressed to IPv6 multicast groups that have no members on the local subnet. In this case, the
Router-Alert option carried in the IPv6 multicast packets is useful for the router to make a decision
whether to deliver the IPv6 multicast packets to the upper-layer protocol for processing. For details
about the Router-Alert option, refer to RFC 2113.
An MLD message is processed differently depending whether it carries the Router-Alert option in the
IPv6 header:
z By default, in consideration of compatibility, the device does not check the Router-Alert option,
that is, it processes all received MLD messages. In this case, the device passes MLD messages
to the upper layer protocol for processing, no matter whether the MLD messages carry the
Router-Alert option or not.
z To enhance the device performance, avoid unnecessary costs, and ensure the protocol security,
you can configure the device to discard MLD messages without the Router-Alert option.
Configuring the Router-Alert option for MLD messages globally
Follow these steps to configure the Router-Alert option for MLD messages globally:
To do… Use the command… Remarks
Enter system view system-view —
Enter MLD view mld —
Configure the interface to discard
any MLD message without the
Router-Alert option
require-router-alert
Optional
By default, the device does not
check MLD messages for the
Router-Alert option.