Specifications

CHAPTER

18-1

Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide

78-11380-07

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.

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 Release 12.1.

This chapter consists of these sections:

• Understanding IGMP Snooping, page 18-1

• Configuring IGMP Snooping, page 18-5

• Displaying IGMP Snooping Information, page 18-10

• Understanding Multicast VLAN Registration, page 18-13

• Configuring MVR, page 18-15

• Displaying MVR Information, page 18-19

• Configuring IGMP Filtering, page 18-20

• Displaying IGMP Filtering Configuration, page 18-24

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 ofmulticast 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,