31.2.2 MLD operation

(1) MLDv1 operation

The following table describes the specifications that the Switch supports for MLDv1 messages.

Table 31-1 MLDv1 messaging

Type		Meaning	Supported
			Sending	Receiving
Multicast Listener Query	General Query	Query to check the hosts that have joined the IPv6 multicast group (query to all groups)	OK	OK
	Group-Specific Query	Query to check the hosts that have joined the IPv6 multicast group (query to a specific group)	OK	OK
Multicast Listener Report		Report on the IPv6 multicast group the host has joined	NG	OK
Multicast Listener Done		Report on the IPv6 multicast group the host has left	NG	OK

(2) MLDv2 operation

MLDv2 enables source filtering functionality by specifying a filter mode and sender list. There are two filter modes:

• INCLUDE: Only packets from senders included in the specified sender list are forwarded.

• EXCLUDE: Only packets from senders that are not included in the specified sender list are forwarded.

The following table describes the specifications that the Switch supports for MLDv2 messages.

Table 31-2 MLDv2 messaging

Type		Meaning	Supported
			Sending	Receiving
Version 2 Multicast Listener Query	General Query	Query to check the hosts that have joined the IPv6 multicast group (query to all groups)	OK	OK
	Multicast Address Specific Query	Query to check the hosts that have joined the IPv6 multicast group (query to a specific group)	OK	OK
	Multicast Address and Source Specific Query	Query to check the hosts that have joined the IPv6 multicast group (query to a specific sender and group)	OK	OK
Version 2 Multicast Listener Report	Current State Report	Report on the IPv6 multicast group and the filter mode of the host	NG	OK
	State Change Report	Report on the changes to the IPv6 multicast group and filter mode of the host	NG	OK

The filter mode and sender list can be changed after the host has joined a group by changing the Multicast Address Record specification in a Report message. The following table describes the Multicast Address Record types supported by the Switch.

Table 31-3 Multicast Address Record Types

Type		Meaning	Supported
Current State Report	MODE_IS_INCLUDE	Indicates that the mode is INCLUDE	OK
	MODE_IS_EXCLUDE	Indicates that the mode is EXCLUDE	OK (the sender list is disregarded)
State Change Report	CHANGE_TO_ INCLUDE_MODE	Indicates that the filter mode has changed to INCLUDE	OK
	CHANGE_TO_ EXCLUDE_MODE	Indicates that the filter mode has changed to EXCLUDE	OK (the sender list is disregarded)
	ALLOW_NEW_ SOURCES	Indicates that a sender wishing to receive data has been added	OK
	BLOCK_OLD_ SOURCES	Indicates that a sender wishing to receive data has been deleted	OK

The following describes MLDv1 operation that uses MLDv1 messages:

• IPv6 multicast routers regularly send a Multicast Listener Query message to a link-local address ff02::1 for all nodes to obtain information about IPv6 multicast membership on directly connected interfaces.

• When a host receives a Multicast Listener Query, it sends a Multicast Listener Report to the corresponding group to report the join status to the group.

• When a Multicast Listener Report is received from a host, the IPv6 multicast router adds the group to the membership list.

• When a Multicast Listener Done message is received, the group is deleted from the membership list.

The following figure shows how MLDv1 groups are joined and left.

Figure 31-2: MLDv1 Join/Leave Operation

The following describes MLDv2 operation that uses MLDv2 messages:

• IPv6 multicast routers regularly send a Version 2 Multicast Listener Query (General Query) message to the link-local address ff02::1 for all nodes to obtain information about IPv6 multicast membership on directly connected interfaces.

• When a host receives a Version 2 Multicast Listener Query, it sends a Version 2 Multicast listener Report (Current State Report) to ff02::16 to report the join status to the group.

• When an IPv6 multicast router receives a Version 2 Multicast Listener Report (State Change Report) message from a host, the router adds or removes the group from the membership list based on the Multicast Address Record type.

The following figure shows how MLDv2 Report messages are sent from hosts.

Figure 31-3: MLDv2 Join/Leave Operation