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your switch (page 3-227). This interface will then join all the current
multicast groups supported by the attached router/switch to ensure that
multicast traffic is passed to all appropriate interfaces within the switch.
Static IGMP Host Interface – For multicast applications that you need to
control more carefully, you can manually assign a multicast service to
specific interfaces on the switch (page 3-229).
Configuring IGMP Snooping and Query Parameters
You can configure the switch to forward multicast traffic intelligently.
Based on the IGMP query and report messages, the switch forwards traffic
only to the ports that request multicast traffic. This prevents the switch
from broadcasting the traffic to all ports and possibly disrupting network
performance.
Command Usage
• IGMP Snooping – This switch can passively snoop on IGMP Query
and Report packets transferred between IP multicast routers/switches
and IP multicast host groups to identify the IP multicast group
members. It simply monitors the IGMP packets passing through it,
picks out the group registration information, and configures the
multicast filters accordingly.
• IGMP Querier – A router, or multicast-enabled switch, can
periodically ask their hosts if they want to receive multicast traffic. If
there is more than one router/switch on the LAN performing IP
multicasting, one of these devices is elected “querier” and assumes the
role of querying the LAN for group members. It then propagates the
service requests on to any upstream multicast switch/router to ensure
that it will continue to receive the multicast service.
Note: Multicast routers use this information, along with a multicast
routing protocol such as DVMRP or PIM, to support IP
multicasting across the Internet.