CHAPT ER
27-1
Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-21521-01
27
Configuring IPv6 MLD Snooping
You can use Multicast Listener Discovery (MLD) snooping to enable efficient distribution of IP
Vers io n 6 (IPv6) multicast data to clients and routers in a switched network on the Catalyst 3750-X or
3560-X switch. Unless otherwise noted, the term switch refers to a Catalyst 3750-X or 3560-X
standalone switch and to a Catalyst 3750-X switch stack.
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 {default |
routing | vlan} global configuration command.
Note On switches running the LAN base feature set, the routing template is not supported.
For related information, see these chapters:
For more information about SDM templates, see Chapter 8, “Configuring SDM Templates.”
For information about IPv6 on the switch, seeChapter 43, “Configuring IPv6 Unicast Routing.”.
Note For complete syntax and usage information for the commands used in this chapter, see the command
reference for this release or the Cisco IOS documentation referenced in the procedures.
This chapter includes these sections:
“Understanding MLD Snooping” section on page 27-1
“Configuring IPv6 MLD Snooping” section on page 27-5
“Displaying MLD Snooping Information” section on page 27-12

Understanding 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.