December 2005 © Foundry Networks, Inc. 18 - 1
Chapter 18
Configuring IP Multicast Traffic Reduction
This chapter describes how to configure IP multicast traffic reduction and PIM SM Traffic Snooping parameters on
a Foundry device.
This chapter contains the following information:
Overview
Foundry Layer 2 Switches and Layer 3 Switches forward all IP multicast traffic by default based on the Layer 2
information in the packets. Optionally, you can enable these Foundry devices to make forwarding decisions in
hardware, based on multicast group by enabling the IP Multicast Traffic Reduction feature.
When this feature is enabled, these Foundry devices examine the MAC address in an IP multicast packet and
forward the packet only on the ports from which the device has received Group Membership reports for that group,
instead of forwarding all multicast traffic to all ports. The device sends traffic for other groups out all ports.
When you enable IP Multicast Traffic Reduction, you also can configure the following features:
• IGMP mode – When you enable IP Multicast Traffic Reduction, the device passively listens for IGMP Group
Membership reports by default. If the multicast domain does not have a router to send IGMP queries to elicit
these Group Membership reports, you can enable the device to actively send the IGMP queries.
• Query interval – The query interval specifies how often the device sends Group Membership queries. This
query interval applies only to the active IGMP mode. The default is 60 seconds. You can change the interval
to a value from 10 – 600 seconds.
• Age interval – The age interval specifies how long an IGMP group can remain in the IGMP group table without
the device receiving a Group Membership report for the group. If the age interval expires before the device
Table 18.1: Chapter Contents
Description See Page
Overview of IP multicast traffic reduction 18-1
Configuring IP multicast traffic reduction 18-2
Enabling PIM SM traffic snooping 18-5
Displaying IP multicast information 18-8
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