Understanding Igmp Snooping - Cisco 2950 - Catalyst Switch Configuration Manual

Configuring IGMP Snooping and MVR
This chapter describes how to configure Internet Group Management Protocol (IGMP) snooping on your
Catalyst 2950 or Catalyst 2955 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 21-1
Configuring IGMP Snooping, page 21-6
Displaying IGMP Snooping Information, page 21-13
Understanding Multicast VLAN Registration, page 21-14
Configuring MVR, page 21-17
Displaying MVR Information, page 21-21
Configuring IGMP Filtering and Throttling, page 21-21
Displaying IGMP Filtering and Throttling Configuration, page 21-27
C H A P T E R
Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
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