3Com Switch 4200G Configuration Guide

29
IGMP SNOOPING CONFIGURATION
Overview of IGMP
Snooping
IGMP Snooping
Fundamentals
IGMP Snooping (Internet Group Management Protocol Snooping) is a multicast
control mechanism running on Layer 2 switch. It is used to manage and control
multicast groups.
When the IGMP messages transferred from the hosts to the router pass through the
Layer 2 switch, the switch uses IGMP Snooping to analyze and process the IGMP
messages.
By listening to IGMP messages, the switch establishes and maintains MAC multicast
address tables at data link layer, and uses the tables to forward the multicast packets
delivered from the router.
As shown in Figure 79, multicast packets are broadcasted at Layer 2 when IGMP
Snooping is disabled and multicasted (not broadcasted) at Layer 2 when IGMP
Snooping is enabled.
Figure 79 Multicast packet transmission with or without IGMP Snooping
Table 219 IGMP message processing on the switch
Received message
type
Sender Receiver Switch processing
IGMP host report
message
Host Switch Add the host to the corresponding
multicast group.
IGMP leave message Host Switch Remove the host from the multicast
group.
Internet
Video stream
VOD server
Layer 2 Ethernet sw itch
Muliticast router
Video stream
Video stream
Video stream
Multic as t
group member
Non-multicast
group member
Non-multicast
group member
Video stream
Video stream
Internet
Video stream
VOD server
Layer 2 Ethernet sw itch
Muliticast router
Video stream
Multicast
group member
Non-multicast
group member
Non-multicast
group member
Video streamVideo stream
Multicast packet transmission
without IGMP Snooping
Multicast packet transmission
with IGMP Snooping
Internet
Video stream
Muliticast
Multic as t
group member
Non-
group member
Non-
group member
Internet
Video stream
Muliticast
Multicast
group member
Non -
group member
Non-
group member
Multicast packet transmission
without IGMP Snooping
Internet
Video stream
VOD server
Layer 2 Ethernet sw itch
Muliticast router
Video stream
Video stream
Video stream
Multic as t
group member
Non-
group member
Non-
group member
Video stream
Video stream
Internet
Video stream
VOD server
Layer 2 Ethernet sw itch
Muliticast router
Video stream
Multicast
group member
Non -
group member
Non-
group member
Video streamVideo stream
Multicast packet transmission
without IGMP Snooping
Multicast packet transmission
with IGMP Snooping
Internet
Video stream
Muliticast
Multic as t
group member
Non-
group member
Non-
group member
Internet
Video stream
Muliticast
Multicast
group member
Non -
group member
Non-
group member
Multicast packet transmission
without IGMP Snooping
Internet
Video stream
VOD server
Layer 2 Ethernet sw itch
Muliticast router
Video stream
Video stream
Video stream
Multic as t
group member
Non-multicast
group member
Non-multicast
group member
Video stream
Video stream
Internet
Video stream
VOD server
Layer 2 Ethernet sw itch
Muliticast router
Video stream
Multicast
group member
Non-multicast
group member
Non-multicast
group member
Video streamVideo stream
Multicast packet transmission
without IGMP Snooping
Multicast packet transmission
with IGMP Snooping
Internet
Video stream
Muliticast
Multic as t
group member
Non-
group member
Non-
group member
Internet
Video stream
Muliticast
Multicast
group member
Non -
group member
Non-
group member
Multicast packet transmission
without IGMP Snooping
Internet
Video stream
VOD server
Layer 2 Ethernet sw itch
Muliticast router
Video stream
Video stream
Video stream
Multic as t
group member
Non-
group member
Non-
group member
Video stream
Video stream
Internet
Video stream
VOD server
Layer 2 Ethernet sw itch
Muliticast router
Video stream
Multicast
group member
Non -
group member
Non-
group member
Video streamVideo stream
Multicast packet transmission
without IGMP Snooping
Multicast packet transmission
with IGMP Snooping
Internet
Video stream
Muliticast
Multic as t
group member
Non-
group member
Non-
group member
Internet
Video stream
Muliticast
Multicast
group member
Non -
group member
Non-
group member
Multicast packet transmission
without IGMP Snooping