KB.15.15

4 Multicast Listener Discovery (MLD) Snooping

NOTE: All commands previously in the Summary of commands table are indexed under the entry

Command syntax.

Overview

Multicast addressing allows one-to-many or many-to-many communication among hosts on a

network. Typical applications of multicast communication include audio and video streaming,

desktop conferencing, collaborative computing, and similar applications.

MLD is an IPv6 protocol used on a local link for multicast group management. MLD operates in a

manner similar to IGMP in IPv4 networks. MLD is enabled per VLAN and is analogous to the IPv4

IGMP protocol.

In the factory default state(MLD disabled), the switch floods all IPv6 multicast traffic it receives on

a given VLAN through all ports on that VLAN except the port receiving the inbound multicast traffic.

Enabling MLD imposes management controls on IPv6 multicast traffic to reduce unnecessary

bandwidth usage. MLD is configured per-VLAN.

MLD snooping is a subset of the MLD protocol that operates at the port level and conserves network

bandwidth by reducing the flooding of multicast IPv6 packets.

MLD can be configured using version 1 (MLDv1) or version 2 (MLDv2). MLDv2 introduces

source-specific multicast in which the only packets delivered to the receiver are those that originate

from a specified source address requested by the receiver. The receiver indicates interest in receiving

traffic to a multicast address and additionally can indicate interest in receiving traffic from only

one specified source sending to that multicast address. This reduces the amount of multicast routing

information that needs to be maintained.

These options are available for MLDv1 and MLDv2:

• Query interval—the time interval between general queries sent by the querier.

• Query Max Response Time—the amount of time to wait for a response to a query.

• Last Member Query Interval—the amount of time the querier waits to receive a response from

members to a group-specific query message. It also specifies the amount of time between

successive group-specific query messages.

• Robustness—the number of times to retry a query.

• Fast Learn—enables the port to learn group information when there is a topology change.

This chapter describes MLD snooping and the CLI commands available for configuring it and for

viewing its status. For introductory information on MLD snooping, see “MLD snooping” (page 79).

Enabling or Disabling MLD Snooping on a VLAN

Several CLI commands are available for configuring MLDv1 and MLDv2 parameters on a switch.

To enable or disable MLD on a VLAN, enter the appropriate command.

Syntax:

[no] ipv6 mld [ enable | disable ]

The no form disables MLD snooping on a VLAN.

NOTE: This command must be issued in a VLAN context.

The command no ipv6 mld deletes the configuration on the VLAN.

The command no ipv6 mld option will remove that option from the

configuration and apply the default if one exists.

68 Multicast Listener Discovery (MLD) Snooping