27-1
27
IGMP Snooping Configuration
Wh n configuring IGMP snooping
e
, go to these sections for information you are interested in:
z
IGMP Snooping Overview
z
Configuring IGMP Snooping
z
Displaying and Maintaining IGMP Snooping
IGMP Snooping Configuration Examples
z
Troubleshooting IGMP Snooping
z
In this manual, the term “router” refers to a router in the generic sense or a Layer 3 Ethernet switch
nning an IP multicast protocol.
ru
IGM
Internet Group Management Protocol Snooping (IGMP Snooping) is a multicast constraining
2 devices to manage and control multicast groups.
Princ
g received IGMP messages, a Layer 2 device running IGMP Snooping establishes
P Snooping Overview
mechanism that runs on Layer
iple of IGMP Snooping
By analyzin
mappings between ports and multicast MAC addresses and forwards multicast data based on these
mappings.
As shown in
Figure 27-1
, when IGMP Snooping is not running on the switch, multicast packets are
broadcast to all devices at Layer 2. When IGMP Snooping is running on the switch, multicast packets for
known multicast groups are multicast to the receivers, rather than broadcast to all hosts, at Layer 2.
However, multicast packets for unknown multicast groups are still broadcast at Layer 2.