Azingo

Addresses in the range 224.0.0.0 through 239.255.255.255 are reserved for multicast communications. Whereas most IP communications are one-to-one (such as a Web browser connecting to a Web server), and some IP communications are broadcast to the local network, such as an Address Resolution Protocol (ARP) request, a relatively small number of communications are multicast to multiple specific listeners.

Often, multicast communications are sent only to other hosts on the local network. For example, Enhanced Interior Gateway Routing Protocol (EIGRP) uses the multicast IP address 224.0.0.10 to allow a router to communicate with a single packet a change in the routing table to all neighboring routers.

However, multicast communications can also be routed between networks. Routed multicasting does not typically work on the Internet, however, private networks can be configured to support multicasting. Private routed multicasting is useful for internal streaming video, for example, to transmit live video of a speech by a company’s president to all employee computers.

The bandwidth used when twelve computers use unicasting to view a 128k streaming video feed. Whereas the relatively low bandwidth used in this example would allow most LANs to support unicasting, a network with hundreds or thousands of computers would be able to support only multicasting live video.