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Cisco IE 2000 Switch Software Configuration Guide
OL-25866-01
Chapter 28 Configuring IGMP Snooping and MVR
Information About IGMP Snooping and MVR
These messages dynamically register for streams of multicast traffic in the multicast VLAN on the
Layer 3 device. Switch B. The access layer switch, Switch A, modifies the forwardi ng 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 IP multicast group addr ess 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, based on the MVR mod e.
Default MVR SettingsMVR Configuration Guidelines and Limitations
Receiver ports can only be access ports; they 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 (MVR group addresses) that can be configured on a
switch (that is, the maximum number of television channels that can be received) is 256.
MVR multicast data received in the source VLAN and leaving from receiver ports has its
time-to-live (TTL) decremented by 1 in the switch.
Because MVR on the switch uses IP multicast addresses instead of MAC multicast addresses,
aliased IP multicast addresses are allowed on the switch. However, if the switch is interoperating
with Catalyst 3550 or Catalyst 3500 XL switches, you should not configure IP addresses that alias
between themselves or with the reserved IP multicast addresses (in the range 224.0.0.xxx).
Do not configure MVR on private VLAN ports.
MVR is not supported when multicast routing is enabled 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.
MVR can coexist with IGMP snooping on a switch.
MVR data received on an MVR receiver port is not forwarded to MVR source port s.
MVR does not support IGMPv3 messages.
Tab l e 28-4 Default MVR Settings
Feature Default Setting
MVR Disabled globally and per interface
Multicast addresses None configured
Query response time 0.5 second
Multicast VLAN VLAN 1
Mode Compatible
Interface (per port) default Neither a receiver nor a source port
Immediate Leave Disabled on all ports