32.1.1 Multicast Overview

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 32-1: Overview of multicast

When multicast is used for transmission, a multicast group address is used for the destination address. The following table describes multicast group addresses.

Table 32-1: Multicast group addresses

Protocol	Address range
IPv4	224.0.0.0~239.255.255.255
IPv6	IPv6 addresses whose highest 8 bits are ff (in hexadecimal)