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Multicast Listener Discovery | 607
Leaving a Multicast Group
A receiver that is no longer interested in traffic for a particular group should leave the group by sending a
Done message to the link-scope all-routers multicast address, FF02::02.
When a Querier receives a Done message, it sends a Multicast-Address-Specific Query addressed to the
relevant multicast group. Hosts still interested in receiving traffic for that group (according to the
suppression mechanism) so that the group table entry is maintained. If no reports are received in response
to the query, the group membership entry is cleared and the router stops forwarding traffic for that group.
MLD version 2
MLD version 2 (MLDv2) adds source-filtering capability. A node can report interest in multicast traffic
only from specific source addresses or from all sources except for specific source addresses. MLDv2 is
backwards compatible with MLD version 1.
There are two types of MLDv2 messages
• Multicast Listener Query — a message sent by the Querier to discover multicast listeners
(Figure 27-2).
• General Query — a query to which all listeners should respond.
• Multicast-Address-Specific Query — a query to which listeners for the specified group should
respond to affirm their membership.
• Multicast-Address-and-Source-Specific Query — a query to determine if there are any listeners
interested in a group and source pair.
• Version 2 Multicast Listener Report — a response to a query indicating listening state or state
changes (Figure 27-3).
Figure 27-2. MLDv2 Multicast Listener Query
Version
(6)
Traffic Class
Flow Label
Payload Length
Next Header
(0)
Hop Limit
(1)
ICMPv6 Packet
Preamble
Start Frame
Delimiter
Destination MAC
Source MAC
Ethernet Type
IPv6 Packet
Padding
MLD 0
02
Type
Code
(0)
Multicast Address
Checksum
C
ode: 130: Multicast Listener Query
131: Multicast Listener Report
132: Multicast Listener Done
FCS
Next Header
(58)
Header Extension
Length
(0)
Options
(Router Alert)
Max. Response
Delay
Reserved
Reserved
S
Querier Robustness
Variable
Querier's Query
Interval Code
N
Source Addresses