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Foundry NetIron M2404C and M2404F Metro Access Switches
Configuring Multicast Layer 2 (Rev. 03)
IGMP Snooping
© 2008 Foundry Networks, Inc.
Page 6 of 43
Note that the device architecture allows the CPU to distinguish IGMP information packets from
other packets for the multicast group. The device recognizes the IGMP packets through its filter
engine. This prevents the CPU from becoming overloaded with multicast frames.
The entry in the multicast forwarding table tells the switching engine to send frames addressed to
the 01:00:5E:01:02:03 multicast MAC address that are not IGMP packets to the host that has
joined the group.
If another host (for example, host D) sends an IGMP join message for the same group (
Figure 4
),
the CPU receives that message and adds the port number of host D to the multicast forwarding
table as shown in
Table 2
.
Figure 4: Second Host Joining a Multicast Group
Table 2: Updated Multicast Forwarding Table Destination Address
MAC Address
Type of Packet
Ports
01:00:5e:01:02:03 IGMP
1/1/1,1/1/4
NOTE
The number of multicast groups is 256.
When Link Aggregation is configured, all the multicast traffic is passed on the master port. For
more information about Link Aggregation refer to chapter “
Configuring Interfaces
”.