Cisco 2950 - Catalyst Switch Configuration Manual page 440

Understanding Multicast VLAN Registration
Figure 21-3 Multicast VLAN Registration Example
Multicast VLAN
SP
MVR eliminates the need to duplicate television-channel multicast traffic for subscribers in each VLAN.
Multicast traffic for all channels is only sent around the VLAN trunk once—only on the multicast
VLAN. Although the IGMP leave and join message in the VLAN to which the subscriber port is
assigned. These messages dynamically register for streams of multicast traffic in the multicast VLAN
on the Layer 3 device. The access layer switch (Switch A) modifies the forwarding behavior to allow the
traffic to be forwarded from the multicast VLAN to the subscriber port in a different VLAN, selectively
allowing traffic to cross between two VLANs.
IGMP reports are sent to the same MAC addresses as the multicast data. The Switch A CPU must capture
all IGMP join and leave messages from receiver ports and forward them to the multicast VLAN of the
source (uplink) port.
Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
21-16
Switch B
SP
SP
SP1
Multicast
data
RP1 RP2 RP3 RP4 RP5 RP6 RP7
Customer
premises
IGMP join
Set-top box
TV
data
TV
RP = Receiver Port
SP = Source Port
Chapter 21
Cisco router
Multicast
server
SP
SP
SP2
Switch A
Hub
Set-top box
PC
TV
Note: All source ports belong to
the multicast VLAN.
Configuring IGMP Snooping and MVR
SP
Multicast
data
78-11380-10