Cisco IE 3000 Software Configuration Manual page 432

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Understanding Multicast VLAN Registration

Multicast VLAN

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.

Cisco IE 3000 Switch Software Configuration Guide

Multicast VLAN Registration Example

RP1 RP2 RP3 RP4 RP5 RP6 RP7

RP = Receiver Port

SP = Source Port

Cisco router

Note: All source ports belong to

the multicast VLAN.

Configuring IGMP Snooping and MVR

Chapters

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