Cisco Catalyst 3550 series Software Configuration Manual page 435

Chapter 20 Configuring IGMP Snooping and MVR
Figure 20-3 Multicast VLAN Registration Example
Multicast VLAN
Catalyst 2950
or 2955
switch
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 (S1 switch) 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 S1 CPU must capture all
IGMP join and leave messages from receiver ports and forward them to the multicast VLAN of the
source (uplink) port.
78-11194-09
Catalyst 3550 switch
SP
SP
Catalyst 3550 switch
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
Cisco router
Multicast
server
SP
SP
SP2
S1
Hub
Set-top box
PC
TV
Note: All source ports belong to
the multicast VLAN.
Catalyst 3550 Multilayer Switch Software Configuration Guide
Understanding Multicast VLAN Registration
Catalyst 2950
or 2955
switch
SP
Multicast
data
20-15