279• Determine the source IPv6 address of MLD multicast-address-specific queries.Enabling MLD snooping querierIn an IPv6 multicast network that runs MLD, a multicast router or Layer 3 multicast switch sends MLDqueries, so that all Layer 3 multicast devices can establish and maintain multicast forwarding entries, inorder to forward multicast traffic correctly at the network layer. This router or Layer 3 switch is called the"MLD querier." For more information about MLD querier, see "Configuring MLD (available only on theS5500-EI)."However, a Layer 2 multicast switch does not support MLD. Therefore, it cannot send MLD generalqueries by default. When you enable MLD snooping querier on a Layer 2 switch in a VLAN wheremulticast traffic is switched only at Layer 2 and no Layer 3 multicast devices are present, the Layer 2switch sends MLD queries, so that multicast forwarding entries can be created and maintained at thedata link layer.IMPORTANT:It is meaningless to configure an MLD snooping querier in an IPv6 multicast network that runs MLD.Although an MLD snooping querier does not participate in MLD querier elections, it might affect MLDquerier elections because it sends MLD general queries with a low source IPv6 address.To enable the MLD snooping querier:Step Command Remarks1. Enter system view. system-view N/A2. Enter VLAN view. vlan vlan-id N/A3. Enable the MLD snoopingquerier. mld-snooping querier Disabled by defaultConfiguring parameters for MLD queries and responsesCAUTION:In the configuration, make sure that the interval for sending MLD general queries is greater than themaximum response delay for MLD general queries. Otherwise, IPv6 multicast members might be deletedby mistake.You can modify the MLD general query interval based on the actual condition of the network.A multicast listening host starts a timer for each IPv6 multicast group that it has joined when it receives anMLD query (general query or multicast-address-specific query). This timer is initialized to a random valuein the range of 0 to the maximum response delay advertised in the MLD query message. When the timervalue decreases to 0, the host sends an MLD report to the IPv6 multicast group.To speed up the response of hosts to MLD queries and avoid simultaneous timer expirations causing MLDreport traffic bursts, you must properly set the maximum response delay.
