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Cisco Catalyst Blade Switch 3130 for Dell Software Configuration Guide
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Chapter23 Configuring IGMP Snooping and MVR
Understanding IGMP Snooping
Figure23-1 Initial IGMP Join Message
Router A sends a general query to the switch, which forwards the query t o ports 2 through 5, which are
all members of the same VLAN. Blade Server 1 wants to join multicast group 224.1.2.3 and multicasts
an IGMP membership report (IGMP join message) to the group. The switch CPU uses the information
in the IGMP report to set up a forwarding-table entry, as shown in Table23-1, that includes the port
numbers of Blade Server 1 and the router.
The switch hardware can distinguish IGMP information packets from other packets for the multicast
group. The information in the table tells the switching engi ne to send frames addressed to the 224.1.2.3
multicast IP address that are not IGMP packets to the router and to the host that has joined the group.
Forwarding
table
CPU
Router A
IGMP report 224.1.2
.3
VLAN
Switching engine
19
0
1357
201772
Blade
Server 1
Blade
Server 2
Blade
Server 3
Blade
Server 4
Table23-1 IGMP Snooping Forwarding Table
Destination Address Type of Packet Ports
224.1.2.3 IGMP 1, 2