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.
The switch can snoop on both MLDv1 and MLDv2 protocol packets and
bridge IPv6 multicast data based on destination IPv6 multicast MAC
addresses. The switch can be configured to perform MLD snooping and
IGMP snooping simultaneously.
What Is Multicast VLAN Registration?
IGMP snooping helps limit multicast traffic when member ports are in the
same VLAN; however, when ports belong to different VLANs, a copy of the
multicast stream is sent to each VLAN that has member ports in the
multicast group. MVR eliminates the need to duplicate the multicast traffic
when multicast group member ports belong to different VLANs.
MVR uses a dedicated multicast VLAN to forward multicast traffic over the
L2 network. Only one MVLAN can be configured per switch, and it is used
only for certain multicast traffic, such as traffic from an IPTV application, to
avoid duplication of multicast streams for clients in different VLANs. Clients
can dynamically join or leave the mutlicast VLAN without interfering with
their membership in other VLANs.
MVR, like IGMP Snooping, allows a layer 2 switch to listen to IGMP
messages to learn about multicast group membership.
There are two types of MVR ports: source and receiver.
Source port is the port where multicast traffic is flowing to. It has to be the
member of so called multicast VLAN.
Receiver port is the port where listening host is connected to the switch. It
can be the member of any VLAN, except multicast VLAN.
There are two configured learning modes of the MVR operation: dynamic and
In the dynamic mode MVR learns existent multicast groups by parsing the
IGMP queries from router on source ports and forwarding the IGMP joins
from the hosts to the router.
Configuring L2 Multicast Features