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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
is no SVI IP address, the switch uses the first available IP address configured on the switch. The first
IP address available appears in the output of the show ip interface privileged EXEC command. The
IGMP snooping querier does not generate an IGMP genera l query if it cannot find an available IP
address on the switch.
• The IGMP snooping querier supports IGMP Versions 1 and 2.
• When administratively enabled, the IGMP snooping querier moves to the nonquerier state if it
detects the presence of a multicast router in the network.
• When it is administratively enabled, the IGMP snooping querier moves to the operationally di sabled
state under these conditions:
–
IGMP snooping is disabled in the VLAN.
–
PIM is enabled on the SVI of the corresponding VLAN.

IGMP Report Suppression

IGMP report suppression is enabled by default. When it is enabled, the switch forwards only one IGMP
report per multicast router query. When report suppression is disabled, all IGMP reports are forwarded
to the multicast routers.
Multicast VLAN Registration
Note To use this feature, the switch must be running the LAN Base image.
Multicast VLAN Registration (MVR) is designed for applicati ons using wide-scale deployment of
multicast traffic across an Ethernet ring-based service-provider network (fo r example, the broadcast of
multiple television channels over a service-provider network). MVR allows a subscriber on a port to
subscribe and unsubscribe to a multicast stream on the network-wide multicast VLAN. It allows the
single multicast VLAN to be shared in the network while subscribers remain in separate VLANs. MVR
provides the ability to continuously send multicast streams in the multicast VLAN, but to isolate the
streams from the subscriber VLANs for bandwidth and security reasons.
MVR assumes that subscriber ports subscribe and unsubscribe (j oin and leave) these multicast streams
by sending out IGMP join and leave messages. These messages can originate from an IGMP
Version-2-compatible host with an Ethernet connection. Although MVR operates on the underlying
mechanism of IGMP snooping, the two features operate independently of each other. One can be enabled
or disabled without affecting the behavior of the other feature. However, if IGMP snooping and MVR
are both enabled, MVR reacts only to join and leave messages from multicast groups configured under
MVR. Join and leave messages from all other multicast groups are managed by IGMP snooping.
The switch CPU identifies the MVR IP multicast streams and their associated IP multicast group in the
switch forwarding table, intercepts the IGMP messages, and modifies the forwarding table to include or
remove the subscriber as a receiver of the multicast stream, even though the re ceivers might be in a
different VLAN from the source. This forwarding behavior selectively allows t raffic to cross between
different VLANs.