Cisco IE-4000 Software Configuration Manual page 757

Configuring IPv6 MLD Snooping
This chapter describes how to configure Multicast Listener Discovery (MLD) snooping on the Cisco Industrial Ethernet
Switches, hereafter referred to as switch. When the switch is running the IP services image, you can use MLD snooping
to enable efficient distribution of IP version 6 (IPv6) multicast data to clients and routers in a switched network.
Note: To use IPv6, you must configure the dual IPv4 and IPv6 Switch Database Management (SDM) template on the
switch. You select the template by entering the sdm prefer dual-ipv4-and-ipv6 global configuration command.
Note: For complete syntax and usage information for the commands used in this chapter, see the documents listed in
the Related Documents, page
This chapter includes the following sections:

Information About MLD Snooping, page 753

Prerequisites, page 756

Guidelines and Limitations, page 756

Default Settings, page 757

Configuring IPv6 MLD Snooping, page 757

Verifying Configuration, page 763

Related Documents, page 765
Information About MLD Snooping
In IP version 4 (IPv4), Layer 2 switches can use Internet Group Management Protocol (IGMP) snooping to limit the flooding
of multicast traffic by dynamically configuring Layer 2 interfaces so that multicast traffic is forwarded to only those
interfaces associated with IP multicast devices. In IPv6, MLD snooping performs a similar function. With MLD snooping,
IPv6 multicast data is selectively forwarded to a list of ports that want to receive the data, instead of being flooded to all
ports in a VLAN. This list is constructed by snooping IPv6 multicast control packets.
MLD is a protocol used by IPv6 multicast routers to discover the presence of multicast listeners (nodes wishing to receive
IPv6 multicast packets) on its directly attached links and to discover which multicast packets are of interest to neighboring
nodes. MLD is derived from IGMP; MLD version 1 (MLDv1) is equivalent to IGMPv2 and MLD version 2 (MLDv2) is
equivalent to IGMPv3. MLD is a subprotocol of Internet Control Message Protocol version 6 (ICMPv6), and MLD
messages are a subset of ICMPv6 messages, identified in IPv6 packets by a preceding Next Header value of 58.
The switch supports two versions of MLD snooping:

MLDv1 snooping detects MLDv1 control packets and sets up traffic bridging based on IPv6 destination multicast
addresses.

MLDv2 basic snooping (MBSS) uses MLDv2 control packets to set up traffic forwarding based on IPv6 destination
multicast addresses.
The switch can snoop on both MLDv1 and MLDv2 protocol packets and bridge IPv6 multicast data based on destination
IPv6 multicast addresses.
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