User's Manual

C HAPTER 4 | Configuring the Switch
MLD Snooping
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The querier will not start or will disable itself after having started if it
detects an IPv6 multicast router on the network.
◆ Compatibility - Compatibility is maintained by hosts and routers
taking appropriate actions depending on the versions of IGMP operating
on these devices within a network. (Options: Range: MLD-Auto, Forced
MLDv1, Forced MLDv2; Default: MLD-Auto)
◆ RV - The Robustness Variable allows tuning for the expected packet
loss on a network. A port will be removed from receiving a multicast
service when no MLD reports are detected in response to a number of
MLD queries. The robustness variable sets the number of queries on
ports for which there is no report. (Range: 1-255; Default: 2)
Routers adopt the robustness value from the most recently received
query. If the querier's robustness variable (QRV) is zero, indicating that
the QRV field does not contain a declared robustness value, the switch
will set the robustness variable to the value statically configured by this
command. If the QRV exceeds 7, the maximum value of the QRV field,
the robustness value is set to zero, meaning that this device will not
advertise a QRV in any query messages it subsequently sends.
◆ QI - The Query Interval is the interval at which General Queries are
sent by the Querier. (Range: 1-255 seconds; Default: 125 seconds)
An MLD general query message is sent by the switch at the interval
specified by this attribute. When this message is received by
downstream hosts, all receivers build an IGMP report for the multicast
groups they have joined.
◆ QRI - The Query Response Interval is the Max Response Time
advertised in periodic General Queries. The QRI applies when the
switch is serving as the querier, and is used to inform other devices of
the maximum time this system waits for a response to general queries.
(Range: 10-31744 tenths of a second; Default: 10 seconds)
◆ LLQI - The Last Listener Query Interval (RFC 3810 – MLDv2 for IP) sets
the interval to wait for a response to a group-specific or group-and-
source-specific query message. The overall time to wait for a response
(Last Member Query Time) is the value assigned to LLQI, multiplied by
the Last Member Query Count (which is fixed at 2). (Range: 1-31744
tenths of a second in multiples of 10; Default: 1 second)
When a multicast host leaves a group, it sends an MLD leave message.
When the leave message is received by the switch, it checks to see if
this host is the last to leave the group by sending out an MLD group-
specific or group-and-source-specific query message, and starts a
timer. If no reports are received before the timer expires, the group
record is deleted, and a report is sent to the upstream multicast router.
A reduced value will result in reduced time to detect the loss of the last
member of a group or source, but may generate more burst traffic.
This attribute will take effect only if MLD snooping proxy reporting is
enabled (see page 153).