2.2.b Explain MLD

Multicast Listener Discovery

MLD is an IPv6 protocol that a host uses to request multicast data for a particular group. Using the information obtained through MLD, the device maintains a list of multicast group or channel memberships on a per-interface basis. The devices that receive MLD packets send the multicast data that they receive for requested groups or channels out the network segment of the known receivers.

MLDv1 is derived from IGMPv2, and MLDv2 is derived from IGMPv3. IGMP uses IP Protocol 2 message types, while MLD uses IP Protocol 58 message types, which is a subset of the ICMPv6 messages.

The MLD process is started automatically on the device. You cannot enable MLD manually on an interface. MLD is automatically enabled when you perform one of the following configuration tasks on an interface:

● Enable PIM6

● Statically bind a local multicast group

● Enable link-local group reports

MLD snooping allows the switch to examine MLD packets and make forwarding decisions based on their content as opposed to just flooding. You can configure the switch to use MLD snooping in subnets that receive MLD queries from either MLD or the MLD snooping querier. MLD snooping constraints IPv6 multicast traffic at Layer 2 by configuring Layer 2 LAN ports dynamically to forward IPv6 multicast traffic only to those ports that want to receive it.

Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 2093-2096).  . Kindle Edition.

http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipmulti_lsm/configuration/xe-3s/imc-lsm-xe-3s-book/ipv6-mcast-mld-xe.html