Understanding Multicast Vlan Registration - Cisco Catalyst 3750-X Software Configuration Manual

Understanding Multicast VLAN Registration

Table 26-4 Commands for Displaying IGMP Snooping Information (continued)
Command
show ip igmp snooping mrouter [vlan vlan-id]
show ip igmp snooping querier [vlan vlan-id]
show ip igmp snooping querier [vlan vlan-id]
detail
For more information about the keywords and options in these commands, see the command reference
for this release.
Understanding Multicast VLAN Registration
Multicast VLAN Registration (MVR) is designed for applications using wide-scale deployment of
multicast traffic across an Ethernet ring-based service-provider network (for 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 (join 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 en abled
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 receivers might be in a
different VLAN from the source. This forwarding behavior selectively allows traffic to cross between
different VLANs.
Catalyst 3750-X and 3560-X Switch Software Configuration Guide
26-16
Purpose
Display information on dynamically learned and manually configured
multicast router interfaces.
When you enable IGMP snooping, the switch automatically
Note
learns the interface to which a multicast router is connected.
These are dynamically learned interfaces.
(Optional) Enter vlan vlan-id to display information for a single VLAN.
Display information about the IP address and receiving port for the
most-recently received IGMP query messages in the VLAN.
(Optional) Enter vlan vlan-id to display information for a single VLAN.
Display information about the IP address and receiving port of the
most-recently received IGMP query message in the VLAN and the
configuration and operational state of the IGMP snooping querier in the
VLAN.
Chapter 26 Configuring IGMP Snooping and MVR
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