Cli: Configuring A Multicast Router Port; Understanding Multicast Vlan Registration - Cisco Catalyst 2950 Software Manual

Chapter 11 Configuring IGMP Snooping and MVR

CLI: Configuring a Multicast Router Port

Beginning in privileged EXEC mode, follow these steps to enable a static connection to a multicast
router:
Command
Step 1
configure terminal
Step 2
ip igmp snooping vlan vlan-id mrouter
{interface interface-id} {learn {cgmp |
pim-dvmrp}}
Step 3 end
Step 4
show ip igmp snooping [vlan vlan-id]
Step 5
show ip igmp snooping mrouter [vlan vlan-id]
Step 6
copy running-config startup-config
For CLI procedures, refer to the Cisco IOS Release 12.1 documentation on Cisco.com for additional
information and CLI procedures.

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 enabled
or disabled without affecting the behavior of the other feature. However, if IGMP snooping and MVR
are both enabled, MVR only reacts 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 MAC addresses 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.
78-11380-03
Purpose
Enter global configuration mode.
Specify the multicast router VLAN ID (1 to 1001).
Specify the interface to the multicast router.
Specify the multicast router learning method:
• cgmp to specify listening for CGMP packets.
pim-dvmrp to specify snooping PIM-DVMRP packets
•
Return to privileged EXEC mode.
Verify that IGMP snooping is enabled on the VLAN interface.
Display information on dynamically learned and manually
configured multicast router interfaces.
(Optional) Save your configuration to the startup configuration.
Catalyst 2950 Desktop Switch Software Configuration Guide
Understanding Multicast VLAN Registration
11-7