H3C Technologies H3C S10500 Series Switches - Manual (Page 354)

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After startup, the MLD querier periodically sends MLD general queries at the MLD query interval to check
for IPv6 multicast group members on the network. You can modify the query interval based on the actual
condition of the network.
The MLDv1 querier sends MLD multicast-address-specific queries at the MLD last listener query interval
when it receives an MLD done message. The MLDv2 querier sends MLD
multicast-address-and-source-specific queries at the MLD last listener query interval when it receives a
multicast group and multicast source mapping change report. The number of queries, or the last listener
query count, equals the robustness variable—the maximum number of packet retransmissions.
A multicast listening host starts a timer for each IPv6 multicast group that it has joined when it receives an
MLD query—general query, multicast-address-specific query, or multicast-address-and-source-specific
query. The 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 decreases to 0, the host sends an MLD
membership report message 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 properly set the maximum response delay.
• For MLD general queries, the maximum response delay is set by the max-response-time command.
• For MLD multicast-address-specific query and multicast-address-and-source-specific query
messages, the maximum response delay equals the last listener query interval.
When multiple multicast routers exist on the same subnet, the MLD querier is responsible for sending MLD
query messages. If a non-querier router receives no MLD query from the querier when the other querier
present interval expires, it considers the querier as having failed and starts a new querier election.
Otherwise, the non-querier resets the other querier present timer.
Configuring MLD query and response parameters globally
Follow these steps to configure MLD query and response parameters globally:
To do… Use the command… Remarks
Enter system view system-view —
Enter MLD view mld —
Configure the MLD querier’s
robustness variable
robust-count robust-value
Required
2 times by default.
A higher robustness variable
makes the MLD querier more
robust but results in a longer IPv6
multicast group timeout time.
Configure the startup query
interval
startup-query-interval interval
Required
By default, the startup query
interval is 1/4 of the “MLD query
interval”.
Configure the startup query count startup-query-count value
Required
By default, the startup query count
is set to the MLD querier’s
robustness variable.
Configure the MLD query interval timer query interval
Required
125 seconds by default.