Cisco Systems A9014CFD manual IPv6 Multicast Groups, IPv6 Multicast Routing Implementation, 42-3

Chapter 42 IPv6 Multicast

Feature Overview

How active a multicast group is, its duration, and its membership can vary from group to group and from time to time. A group that has members may have no activity.

IPv6 Multicast Groups

An IPv6 address must be configured on an interface for the interface to forward IPv6 traffic. Configuring

asite-local or global IPv6 address on an interface automatically configures a link-local address and activates IPv6 for that interface. Additionally, the configured interface automatically joins the following required multicast groups for that link:

•Solicited-node multicast group FF02:0:0:0:0:1:FF00::/104 for each unicast and anycast address assigned to the interface

•All-nodes link-local multicast group FF02::1

•All-routers link-local multicast group FF02::2

IPv6 Multicast Routing Implementation

The Cisco IOS software supports the following protocols to implement IPv6 multicast routing:

•MLD for IPv6: MLD is used by IPv6 routers to discover multicast listeners (nodes that want to receive multicast packets destined for specific multicast addresses) on directly attached links. There are two versions of MLD:

–MLD version 1 is based on version 2 of the IGMP for IPv4

–MLD version 2 is based on version 3 of the IGMP for IPv4.

•IPv6 multicast for Cisco IOS software uses both MLD version 2 and MLD version 1. MLD version 2 is fully backward-compatible with MLD version 1 (described in RFC 2710). Hosts that support only MLD version 1 interoperates with a router running MLD version 2. Mixed LANs with both MLD version 1 and MLD version 2 hosts are likewise supported.

•PIM is used between routers so that they can track which multicast packets to forward to each other and to their directly connected LANs.

•PIM in PIM SSM has the additional ability to report interest in receiving packets from specific source addresses (or from all but the specific source addresses) to an IP multicast address.

Multicast Listener Discovery Protocol for IPv6

To start implementing multicasting in a network, users must first define who receives the multicast. The MLD protocol is used by IPv6 devices to discover the presence of multicast listeners (for example, nodes that want to receive multicast packets) on their directly attached links, and to discover specifically which multicast addresses are of interest to those neighboring nodes. It is used for discovering local group and source-specific group membership. The MLD protocol provides a means to automatically control and limit the flow of multicast traffic throughout your network with the use of special multicast queriers and hosts.

The differences between multicast queriers and hosts are as follows:

•A querier is a network device that sends query messages to discover which network devices are members of a given multicast group.

•A host is a receiver that send report messages to inform the querier of a host membership.

	Cisco ASR 901 Series Aggregation Services Router Software Configuration Guide
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