Multicast VLAN Registration

Multicast VLAN Registration (MVR) is designed to support distributing multicast streams for IPTV to subscribers over a Layer 2 network. In a standard Layer 2 network, a multicast stream received on a VLAN is not forwarded to another VLAN. The streams are confined to the Layer 2 broadcast domain. In an IGMP snooping environment, streams are forwarded only to interested hosts on a VLAN. For inter-VLAN forwarding (routing) a multicast routing protocol, such as PIM/DVMRP must be deployed.

MVR breaks this basic rule, so that a stream received over Layer 2 VLANs is forwarded to another VLAN, eliminating the need for a Layer 3 routing protocol. It simplifies the multicast stream distribution and is a better solution for IPTV-like services. With MVR, a multicast stream is forwarded to all VLANs containing interested hosts.

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Standard VLAN Compared to an MVR VLAN

In the above figure, the left side shows a standard VLAN carrying a multicast stream.

The host H1 receives the multicast stream because it resides on VLAN Vlan1, but host H2 does not receive the multicast traffic because no IP multicast routing protocol forwards the stream to VLAN Vlan2. On the right side of the figure, H2 does receive the multicast stream. Because Vlan1 was configured as an MVR VLAN, the multicast stream is forwarded to the other VLANs on the switch. containing hosts that have requested the stream. To configure a VLAN as an MVR VLAN, use the following command: configure mvr add vlan vlan-name

Typically, IGMP snooping is enabled, so only hosts that have requested a stream can see the multicast traffic. For example, another host on VLAN2 cannot receive the traffic unless it has sent an IGMP request to be included in the group.

Notice that only VLAN1 is MVR enabled. Configure MVR only on the ingress VLAN. To enable MVR on the switch, use the following command: enable mvr