IPv6 Multicast Overview

IPv6 defines three types of addresses: unicast, anycast, and multicast. Each type of address enables a device to send datagrams to selected recipients:

• A unicast address enables a device to send a datagram to a single recipient.
• An anycast address enables a device to send a datagram to one recipient out of a set of recipients.
• A multicast address enables a device to send a datagram to a specified set of hosts, known as a multicast group, in different subnetworks.

IPv6 multicast improves network efficiency by allowing a host to transmit a datagram to a targeted group of receivers. For example, a host may want to send a large video clip to a group of selected recipients. It would be time-consuming for the host to unicast the datagram to each recipient individually. If the host broadcasts the video clip throughout the network, network resources are not available for other tasks. The host uses only the resources it needs when multicasting the datagram.

Routers use multicast routing algorithms to determine the best route and transmit multicast datagrams throughout the network. E-series routers support a number of IPv6 multicast protocols on virtual routers (VRs). Each VR handles the interoperability of IPv6 multicast protocols automatically. To start IPv6 multicast operation on a VR, you access the context for that VR and configure the desired protocols on the selected interfaces. Table 9 describes the function of each the protocol that the router supports.

Table 9: Function of Multicast Protocols on a Router

The router supports up to 16,384 multicast forwarding entries (multicast routes) at any time.

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