Cisco Systems 3750E manual Configuring MVR, Default MVR Configuration, Mvr, 24-20

Chapter 24 Configuring IGMP Snooping and MVR

Configuring MVR

When a subscriber changes channels or turns off the television, the set-top box sends an IGMP leave message for the multicast stream. The switch CPU sends a MAC-based general query through the receiver port VLAN. If there is another set-top box in the VLAN still subscribing to this group, that set-top box must respond within the maximum response time specified in the query. If the CPU does not receive a response, it eliminates the receiver port as a forwarding destination for this group.

Without Immediate Leave, when the switch receives an IGMP leave message from a subscriber on a receiver port, it sends out an IGMP query on that port and waits for IGMP group membership reports. If no reports are received in a configured time period, the receiver port is removed from multicast group membership. With Immediate Leave, an IGMP query is not sent from the receiver port on which the IGMP leave was received. As soon as the leave message is received, the receiver port is removed from multicast group membership, which speeds up leave latency. Enable the Immediate-Leave feature only on receiver ports to which a single receiver device is connected.

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. The IGMP leave and join messages are 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. Switch B. The access layer switch, Switch A, modifies the forwarding 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 address 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 mode.

Configuring MVR

These sections contain this configuration information:

•Default MVR Configuration, page 24-20

•MVR Configuration Guidelines and Limitations, page 24-21

•Configuring MVR Global Parameters, page 24-21

•Configuring MVR Interfaces, page 24-22

Default MVR Configuration

Table 24-5shows the default MVR configuration.

Table 24-5	Default MVR Configuration
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

	Catalyst 3750-E and 3560-E Switch Software Configuration Guide
24-20	OL-9775-02