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Multimedia Traffic Control with IP Multicast (IGMP)
More on IGMP Operation
PC X
Video
Server
Router
Router
PC 1:
Video
Client
Switch 1
Router
Router
Switch 2
PC 2
PC 3
PC 5
PC 6
Multicast Data Stream
IGMP is NOT
running here.
IGMP IS
running here.
PC 4:
Video
Client
Figure 12-3. The Advantage of Using IGMP
The next figure (12-4) shows a network running IP multicasting using IGMP
without a multicast router. In this case, the IGMP-configured switch runs as a
querier.
PCs 2, 5, and 6 are members of the same IP multicast group.
IGMP is configured on switches 3 and 4. Either of these switches can operate
as querier because a multicast router is not present on the network. (If an
IGMP switch does not detect a querier, it automatically assumes this role,
assuming the querier feature is enabledthe defaultwithin IGMP, and that
the switch has an IP address on the IGMP-enabled VLAN.)
12-12