Mld Messages; Mld Queries - Cisco IE-4000 Software Configuration Manual

Configuring IPv6 MLD Snooping
Information About MLD Snooping
Note: The switch does not support MLDv2 enhanced snooping (MESS), which sets up IPv6 source and destination
multicast address-based forwarding.
MLD snooping can be enabled or disabled globally or per VLAN. When MLD snooping is enabled, a per-VLAN IPv6
multicast MAC address table is constructed in software and a per-VLAN IPv6 multicast address table is constructed in
software and hardware. The switch then performs IPv6 multicast-address based bridging in hardware.
These sections describe some parameters of IPv6 MLD snooping:

MLD Messages, page 754

MLD Queries, page 754

Multicast Client Aging Robustness, page 755

Multicast Router Discovery, page 755

MLD Reports, page 755

MLD Done Messages and Immediate-Leave, page 756

Topology Change Notification Processing, page 756

MLD Messages

MLDv1 supports three types of messages:

Listener Queries are the equivalent of IGMPv2 queries and are either General Queries or Multicast-Address-Specific
Queries (MASQs).

Multicast Listener Reports are the equivalent of IGMPv2 reports.

Multicast Listener Done messages are the equivalent of IGMPv2 leave messages.
MLDv2 supports MLDv2 queries and reports, as well as MLDv1 Report and Done messages.
Message timers and state transitions resulting from messages being sent or received are the same as those of IGMPv2
messages. MLD messages that do not have valid link-local IPv6 source addresses are ignored by MLD routers and
switches.

MLD Queries

The switch sends out MLD queries, constructs an IPv6 multicast address database, and generates MLD group-specific
and MLD group-and-source-specific queries in response to MLD Done messages. The switch also supports report
suppression, report proxying, Immediate-Leave functionality, and static IPv6 multicast MAC-address configuration.
When MLD snooping is disabled, all MLD queries are flooded in the ingress VLAN.
When MLD snooping is enabled, received MLD queries are flooded in the ingress VLAN, and a copy of the query is sent
to the CPU for processing. From the received query, MLD snooping builds the IPv6 multicast address database. It detects
multicast router ports, maintains timers, sets report response time, learns the querier IP source address for the VLAN,
learns the querier port in the VLAN, and maintains multicast-address aging.
Note: When the IPv6 multicast router is a Catalyst 6500 switch and you are using extended VLANs (in the range 1006 to
4094), IPv6 MLD snooping must be enabled on the extended VLAN on the Catalyst 6500 switch in order for this switch
to receive queries on the VLAN. For normal-range VLANs (1 to 1005), it is not necessary to enable IPv6 MLD snooping
on the VLAN on the Catalyst 6500 switch.
When a group exists in the MLD snooping database, the switch responds to a group-specific query by sending an MLDv1
report. When the group is unknown, the group-specific query is flooded to the ingress VLAN.
754