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IGMP Snooping 125
Figure 29 Multicast Packet Transmission With IGMP Snooping
Implement IGMP Snooping
This section introduces related switch concepts of IGMP Snooping:
■ Router Port: The port directly connected to the multicast router.
■ Multicast member port: The port connected to the multicast member. The
multicast member refers to a host that joined a multicast group.
■ MAC multicast group: The multicast group is identified with MAC multicast
address and maintained by the Switch 7750.
■ Router port aging time: Time set on the router port aging timer. If the switch
has not received any IGMP general query messages before the timer times out,
it is no longer considered a router port.
■ Multicast group member port aging time: When a port joins an IP multicast
group, the aging timer of the port begins timing. If the switch has not received
any IGMP report messages before the timer times out, it transmits IGMP
specific query message to the port.
■ Maximum response time: When the switch transmits IGMP specific query
message to the multicast member port, the Switch 7750 starts a response
timer, which times before the response to the query. If the switch has not
received any IGMP report message before the timer times out, it will remove
the port from the multicast member ports
The Switch 7750 runs IGMP Snooping to listen to the IGMP messages and map
the host and its ports to the corresponding multicast group address. To implement
IGMP Snooping, Switch 7750 processes different IGMP messages shown in the
figure below:
Video stream
Video stream
Video
stream
Video stream
Video stream
VOD server
Internet/Intranet
Multicast router
Layer 2
Ethernet switch
Multicast
group
member
Nonmulticast
group
member
Nonmulticast
group
member