H3C Technologies H3C S12500 Series Switches - Manual (Page 312)

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maintain multicast forwarding entries, in order 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."
However, a Layer 2 multicast switch does not support MLD and it cannot send MLD general queries by
default. In a network where multicast traffic is only switched at the data link layer and no Layer 3 multicast
devices are present, you can enable MLD snooping querier on a Layer 2 switch so that the Layer 2 switch
can send MLD queries periodically and establish and maintain multicast forwarding entries for IPv6
multicast forwarding at the data link layer.
IMPORTANT:
Do not configure an MLD snooping querier in an IPv6 multicast network running MLD. Although an MLD
snooping querier does not take part in MLD querier elections, it might affect MLD querier elections
because it sends MLD general queries with a low source IPv6 address.
To enable the MLD snooping querier:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter VLAN view. vlan vlan-id N/A
3. Enable the MLD snooping
querier.
mld-snooping querier Disabled by default.
Configuring parameters for MLD queries and responses
CAUTION:
Make sure the MLD query interval is greater than the maximum response delay for MLD general queries.
Otherwise, undesired deletion of IPv6 multicast members might occur.
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 an
MLD query (general query or multicast-address-specific query). This timer is initialized to a random value
in the range of 0 to the maximum response delay advertised in the MLD query message. When the timer
value 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 MLD
report traffic bursts, you must correctly set the maximum response delay.
• The maximum response delay for MLD general queries is set by the max-response-time command.
• The maximum response delay for MLD multicast-address-specific queries equals the MLD
last-listener query interval.
Configuring the global parameters for MLD queries and responses
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter MLD-snooping view. mld-snooping N/A