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Determine the MLD general query interval
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Determine the MLD last-member query interval
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Determine the maximum response time for MLD general queries
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Determine the source IPv6 address of MLD general queries
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Determine the source IPv6 address of MLD multicast-address-specific queries
Enabling MLD snooping querier
In an IPv6 multicast network that is running MLD, a multicast router or Layer 3 multicast switch sends
periodic MLD general queries, so that all Layer 3 multicast devices can establish and 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."
However, a Layer 2 multicast switch does not support MLD, and therefore cannot send MLD general
queries by default. By enabling MLD snooping querier on a Layer 2 switch in a VLAN where multicast
traffic must be Layer-2 switched only and no Layer 3 multicast devices are present, the Layer 2
switch will act as the MLD querier to send periodic MLD queries. Multicast forwarding entries can
then be created and maintained at the data link layer.
Follow these steps to enable the MLD snooping querier:
To do...
Use the command...
Remarks
Enter system view
system-view
—
Enter VLAN view
vlan
vlan-id
—
Enable the MLD snooping querier
mld-snooping querier
Required
Disabled by default
NOTE:
It is meaningless to 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.
Configuring MLD queries and responses
You can tune the MLD general query interval based on the actual condition of the network.
Upon receiving an MLD query—general query or multicast-address-specific query, a host starts a
timer for each IPv6 multicast group that it has joined. This timer is initialized to a random value in the
range of 0 to the maximum response time—the host obtains the value of the maximum response
time from the Max Response Time field in the MLD query that it received. When the timer value
comes down to 0, the host sends an MLD report to the corresponding IPv6 multicast group.
An appropriate setting of the maximum response time for MLD queries enables hosts to respond to
queries quickly and avoids bursts of MLD traffic on the network. Such burst can occur when a large
number of hosts simultaneously send reports after the corresponding timers expire simultaneously.
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For MLD general queries, configure the maximum response time to fill their Max Response time
field.
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For MLD multicast-address-specific queries, configure the MLD last-member query interval to
fill their Max Response time field. Namely, for MLD multicast-address-specific queries, the
maximum response time equals the MLD last-member query interval.
Configuring MLD queries and responses globally
Follow these steps to configure MLD queries and responses globally: