Multicast Vlan Registration - NETGEAR M4200 Software Administration Manual

Multicast VLAN Registration

The IGMP Layer 3 protocol is widely used for IPv4 network multicasting. In Layer 2 networks,
the IGMP protocol uses resources inefficiently. For example, a Layer 2 switch multicast traffic
to all ports even if there are receivers connected to only a few ports.
To fix this problem, the IGMP snooping protocol was developed. But the problem reappears
when receivers are in different VLANs. Multicast VLAN registration (MVR) is intended to
solve the problem of receivers in different VLANs. It uses a dedicated manually configured
VLAN, called the multicast VLAN, to forward multicast traffic over Layer 2 network in
conjunction with IGMP snooping.
MVR, like the IGMP Snooping protocol, allows a Layer 2 switch to snoop on the IGMP control
protocol. Both protocols operate independently of each other. Both protocols can be enabled
on the switch interfaces at the same time. In such a case, MVR listens to the join and report
messages only for groups configured statically. All other groups are managed by IGMP
snooping.
There are two types of MVR ports: source and receiver.
• The source port is the port to which the multicast traffic flows using the multicast VLAN.
• The receiver port is the port where a listening host is connected to the switch. It can utilize
any (or no) VLAN, except the multicast VLAN. This implies that the MVR switch performs
VLAN tag substitution from the multicast VLAN source port to the VLAN tag used by the
receiver port.
The multicast VLAN is the VLAN that you configure in the specific network for MVR purposes.
The multicast VLAN is used to transfer multicast traffic over the network to avoid duplication
of multicast streams for clients in different VLANs. The operator must configure the multicast
VLAN manually for all source ports in the network. A diagram of a network configured for
MVR is shown in the following illustration. SP is the source port and RP is the receiver port.
Managed Switches
MVR
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