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24 Description of IGMP Snooping and MLD Snooping
24.1 Overview of IGMP snooping and MLD snooping
This section gives an overview of multicast, IGMP snooping, and MLD snooping.
24.1.1 Overview of multicast
When the same information is sent by unicast to multiple recipients, the load increases for
both the sender and the network because the sender replicates and sends data for each
recipient. With multicast, on the other hand, the sender sends data to a selected group
within the network. Because the sender does not need to replicate data for each recipient,
network load can be reduced regardless of the number of recipients. The following figure
gives an overview of multicast.
Figure 24-1 Overview of multicasting
When multicast is used for transmission, a multicast group address is used for the
destination address. The following table describes multicast group addresses.
Table 24-1 Multicast group address
Protocol
IPv4
IPv6
24.1.2 Overview of IGMP snooping and MLD snooping
Layer 2 switches forward multicast traffic to all ports within a VLAN. Therefore, when
434
Address range
224.0.0.0 to 239.255.255.255
IPv6 addresses whose highest 8 bits are ff (in hexadecimal)
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