IP Multicast

This section briefly covers the IP multicast areas of interest for the CCIE written test.

The multicasting protocol was designed to reduce the high bandwidth requirements of technologies, such as video on demand, to a single stream of information to more than one device. Applications include electronic learning, company share meetings (video on demand), and software distribution.

Multicasting transmits IP packets from a single source to multiple destinations. The network device transmitting the multicast source copies single packets, which are sent to a subset of network devices. In IPv4, the Class D addresses ranging from to are reserved for multicast. Routing protocols, for example, use multicasting to send Hello packets and establish neighbor adjacencies.

Table 1-16 displays some common multicast addresses and their uses. Table 1-16 Class D Multicast Address Examples

Multicast Address


All hosts on subnets

All multicast routers

All OSPF-enabled routers

All OSPF DR routers

All RIPv2-enabled routers

All EIGRP-enabled routers

TIP The Class D addresses used in multicast traffic range from to

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