MLD

The Multicast Listener Discovery (MLD) protocol is integral to the operation of Internet Protocol Version 6 (IPv6). MLDv1 is defined by RFC 2710, while MLDv2 is defined by RFC 3810. The MLD operations are based on operations similar to the Internet Group Management Protocol (IGMP) that supports IPv4. MLDv2 corresponds to IGMPv3. Both versions are supported by the protocol server.

An IPv6 router uses MLD to: (1) discover multicast listeners (nodes) on the directly attached links, and (2) find out which multicast addresses those nodes have interest in. In MLDv2, nodes can indicate interest in listening to packets that are sent to a specific multicast address from a filtered group of source IP addresses. This filtering can be based on `all but' (Excluding) or `only' (Including) certain source addresses. Host nodes can only be multicast `listeners,' while the multicast routers can act as routers or listeners.