Dell Networking 7048 - What Is Multicast VLAN Registration

708 Configuring L2 Multicast Features
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
compatible.
• 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.
• In the compatible mode MVR does not learn multicast groups, but they
have to be configured by administrator and protocol does not forward joins
from the hosts to the router. To work in this mode the IGMP router has to
be configured to transmit required multicast streams to the network with
the MVR switch.
Enabling MVR and IGMP on the Same Interface
MVR and IGMP snooping operate independently and can both be enabled on
an interface. When both MVR and IGMP snooping are enabled, MVR listens
to the IGMP join and report messages for static multicast group information,
and IGMP snooping manages dynamic multicast groups.