CHAPTER
17-1
Catalyst 2950 Desktop Switch Software Configuration Guide
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17

Configuring IGMP Sno oping an d MVR

This chapter describes how to configure Internet Group Management Protocol (IGMP) snooping on your
switch, including an application of local IGMP snooping, Multicast VLAN Registration (MVR). It also
include s procedur es for con trolling mu lticast group memb ershi p 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 Re lease 12. 1.
This chapter consists of these sections:
Understa ndin g IG MP Snoo ping, p ag e 17- 1
Configuring I GMP Snoop ing, page 17-5
Display ing IGMP Snoopi ng Informa tion, p age 17-11
Understanding Multicast VLAN Registration, page 17-13
Configuring M V R, pa ge 1 7-1 5
Display ing MVR Inf ormatio n, page 17-1 9
Configuring I GMP Filte ring, p age 17-20
Display ing IGMP Filteri ng Configuration , page 17-24
Note For MAC addresses that map to IP multicast groups, you can either manage them through features such
as IGMP snoop ing an d MVR, or you can use static MAC addresses. However, you cannot use both
method s simultaneou sly. Therefo re, befor e using IGMP snoo ping or MVR, you should remove all
static ally configur ed MAC addresses th at map to IP mu lticast gr oups.

Understandin g IGMP Snooping

Layer 2 switc he s ca n u se IG MP snoop in g to c ons trai n t he flo odin g o fm ulti ca st t raffic by dynam ica ll y
configuring Layer 2 interfaces so that multicast traffic is forwarded to only those interfaces associated
with IP mul ticast devices. As the name im plies, IGMP snooping re quires the LAN swi tch to snoop o n
the IGM P t ran smi ssion s bet wee n the ho st a nd t he ro ut er a nd to keep t rac k of mul ticas t gr oups and
member p orts. Wh en the swi tc h r ece ives an IGMP re por t fr om a ho st fo r a pa rti cul ar m ul tica st gr oup ,