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Configuring IGMP Snooping
This chapter describes how to configure Internet Group Management Protocol (IGMP) snooping on the
Catalyst 2928 switch. It also includes procedures for controlling multicast group membership by using
IGMP filtering and procedures for configuring the IGMP throttling action.
For complete syntax and usage information for the commands used in this chapter, see the switch
Note
command reference for this release and the "IP Multicast Routing Commands" section in the Cisco IOS
IP Command Reference, Volume 3 of 3:Multicast, Release 12.2.
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You can either manage IP multicast group addresses through features such as IGMP snooping, or you
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can use static IP addresses.
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,
the switch adds the host port number to the forwarding table entry; when it receives an IGMP Leave
Group message from a host, it removes the host port from the table entry. It also periodically deletes
entries if it does not receive IGMP membership reports from the multicast clients.
For more information on IP multicast and IGMP, see RFC 1112 and RFC 2236.
Note
OL-23389-01
Understanding IGMP Snooping, page 21-1
Configuring IGMP Snooping, page 21-6
Displaying IGMP Snooping Information, page 21-14
Configuring IGMP Filtering and Throttling, page 21-16
Displaying IGMP Filtering and Throttling Configuration, page 21-20
C H A P T E R
Catalyst 2928 Switch Software Configuration Guide
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Troubleshooting
