11-14
Catalyst 3550 Multilayer Switch Software Configuration Guide
78-11194-03
Chapter11 Configuring IGMP Snooping and MVR
Configuring MVR
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 forwa rding b ehavio r to a llo w
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.
Configuring MVR
These sections include basic MVR configuration information:
•Configuration Guidelines and Limitations, page 11-14
•Default MVR Configuration, page 11-15
•Configuring MVR Global Parameters, page 11-15
•Configuring MVR Interfaces, page 11-16

Configuration Guidelines and Limitations

Follow these guidelines when configuring MVR:
•Receiver ports cannot be trunk ports. Receiver ports on a switch can be in different VLANs, but
should not belong to the multicast VLAN.
•The maximum number of multicast entries that can be configured on a switch (that is, the maximum
number of television channels that can be received) is 256.
•Each channel is one multicast stream destined for a unique IP multicast address . These IP addresses
cannot alias between themselves or with the reserved IP multicast addresses (in the
range 224.0.0.xxx).
•Multicast routing and MVR cannot coexist on a switch. If you enable multicast routing and a
multicast routing protocol while MVR is enabled, MVR is disabled, and you receive a warning
message. If you try to enable MVR while multicast routing and a multicast routing protocol are
enabled, the operation to enable MVR is cancelled, and you receive an error message.
Note For complete syntax and usage information for the commands used in this section, refer to the
Catalyst 3550 Multilayer Switch Command Reference for this release.