4000 Router Series IP Multicast Configuration Guide

Configuring IGMP snooping

Feature and hardware compatibility

IGMP snooping is available only on the MSR series routers with Ethernet Layer 2 switching interface

modules. For information about the Ethernet Layer 2 switching interface modules, see HP MSR Router

Series Interface Module Guide.

The term "switch" in this document refers to the MSR series routers with Ethernet Layer 2 switching

interface modules.

Overview

IGMP snooping runs on a Layer 2 switch as a multicast constraining mechanism to improve multicast

forwarding efficiency. It creates Layer 2 multicast forwarding entries from IGMP packets that are

exchanged between the hosts and the router.

As shown in Figure 11, w

hen IGMP snooping is not enabled, the Layer 2 switch floods multicast packets

to all hosts. When IGMP snooping is enabled, the Layer 2 switch forwards multicast packets of known

multicast groups to only the receivers.

Figure 11 Multicast packet transmission without and with IGMP snooping