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40-5
Catalyst 3750 Switch Software Configuration Guide
OL-8550-09
Chapter 40 Configuring IPv6 MLD Snooping
Configuring IPv6 MLD Snooping
Topology Change Notification Processing
When topology change notification (TCN) solicitation is enabled by using the ipv6 mld snooping tcn
query solicit global configuration command, MLDv1 snooping sets the VLAN to flood all IPv6
multicast traffic with a configured number of MLDv1 queries before it begins sending multicast data
only to selected ports. You set this value by using the ipv6 mld snooping tcn flood query count global
configuration command. The default is to send two queries. The switch also generates MLDv1 global
Done messages with valid link-local IPv6 source addresses when the switch becomes the STP root in the
VLAN or when it is configured by the user. This is same as done in IGMP snooping.
MLD Snooping in Switch Stacks
The MLD IPv6 group and MAC address databases are maintained on all switches in the stack, regardless
of which switch learns of an IPv6 multicast group. Report suppression and proxy reporting are done
stack-wide. During the maximum response time, only one received report for a group is forwarded to the
multicast routers, regardless of which switch the report arrives on.
The election of a new stack master does not affect the learning or bridging of IPv6 multicast data;
bridging of IPv6 multicast data does not stop during a stack master re-election. When a new switch is
added to the stack, it synchronizes the learned IPv6 multicast information from the stack master. Until
the synchronization is complete, data ingressing on the newly added switch is treated as unknown
multicast data.
Configuring IPv6 MLD Snooping
These sections describe how to configure IPv6 MLD snooping:
• Default MLD Snooping Configuration, page 40-6
• MLD Snooping Configuration Guidelines, page 40-6
• Enabling or Disabling MLD Snooping, page 40-7
• Configuring a Static Multicast Group, page 40-8
• Configuring a Multicast Router Port, page 40-8
• Enabling MLD Immediate Leave, page 40-9
• Configuring MLD Snooping Queries, page 40-10
• Disabling MLD Listener Message Suppression, page 40-11