Understanding Igmp Snooping - Cisco Catalyst 3550 series Software Configuration Manual

Configuring IGMP Snooping and MVR
This chapter describes how to configure Internet Group Management Protocol (IGMP) snooping on your
Catalyst 3550 switch, including an application of local IGMP snooping, Multicast VLAN Registration
(MVR). It also includes procedures for controlling multicast group membership by using IGMP filtering
and procedures for configuring the IGMP throttling action.
Note For complete syntax and usage information for the commands used in this chapter, refer to the switch
command reference for this release and the Cisco IOS Release Network Protocols Command Reference,
Part 1, for Cisco IOS Release 12.1.
This chapter consists of these sections:
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Note For MAC addresses that map to IP multicast groups, you can either manage them through features such
as IGMP snooping and MVR, or you can use static MAC addresses. However, you cannot use both
methods simultaneously. Therefore, before using IGMP snooping or MVR, you should remove all
statically configured MAC addresses that map to IP multicast groups.

Understanding IGMP Snooping

Layer 2 switches can use IGMP snooping to constrain the flooding of multicast traffic by dynamically
configuring Layer 2 interfaces so that multicast traffic is forwarded to only those interfaces associated
with IP multicast devices. As the name implies, IGMP snooping requires the LAN switch to snoop on
the IGMP transmissions between the host and the router and to keep track of multicast groups and
member ports. When the switch receives an IGMP report from a host for a particular multicast group,
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Understanding IGMP Snooping, page 20-1
Configuring IGMP Snooping, page 20-6
Displaying IGMP Snooping Information, page 20-12
Understanding Multicast VLAN Registration, page 20-13
Configuring MVR, page 20-16
Displaying MVR Information, page 20-20
Configuring IGMP Filtering and Throttling, page 20-21
Displaying IGMP Filtering and Throttling Configuration, page 20-27
C H A P T E R
Catalyst 3550 Multilayer Switch Software Configuration Guide
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