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Cisco ASR 901 Series Aggregation Services Router Software Configuration Guide
OL-23826-09
Chapter 42 IPv6 Multicast
Feature Overview
Prerequisites
• Cisco IOS Release 15.4(1)S or a later release that supports the IPv6 Multicast feature must be
installed previously on the Cisco ASR 901 Series Aggregation Services Router.
• You must first enable IPv6 unicast routing on all interfaces of the device on which you want to
enable IPv6 multicast routing.
Restrictions
• PIM dense-mode is not supported.
• Bidirectional PIM is not supported.
• IGMP and Multicast Listener Discovery (MLD) snooping is not supported.
• You must disable the Source Specific Multicast (SSM) map query dns when static mapping is
configured.
• You must configure the asr901-platf-multicast enable command to enable multicast on the
Cisco ASR 901 router.
• You must enable the asr901-multicast source command on the SVI interface that is connected to
the traffic source.
• Mroute based counter or rate statistics is not supported. The hardware supports only physical
interface based multicast counter and rate statistics.
• Multicast VPN (MVPN) is not supported.
• IPv6 multicast is not supported in VRF lite.
Feature Overview
An IPv6 multicast group is an arbitrary group of receivers that want to receive a particular data stream.
This group has no physical or geographical boundaries—receivers can be located anywhere on the
Internet or in any private network. Receivers that are interested in receiving data flowing to a particular
group must join the group by signaling their local device. This signaling is achieved with the MLD
protocol.
Devices use the MLD protocol to learn whether members of a group are present on their directly attached
subnets. Hosts join multicast groups by sending MLD report messages. The network then delivers data
to a potentially unlimited number of receivers, using only one copy of the multicast data on each subnet.
IPv6 hosts that wish to receive the traffic are known as group members.
Packets delivered to group members are identified by a single multicast group address. Multicast packets
are delivered to a group using best-effort reliability, just like IPv6 unicast packets.
The multicast environment consists of senders and receivers. Any host, regardless of whether it is a
member of a group, can send to a group. However, only the members of a group receive the message.
A multicast address is chosen for the receivers in a multicast group. Senders use that address as the
destination address of a datagram to reach all members of the group.
Membership in a multicast group is dynamic; hosts can join and leave at any time. There is no restriction
on the location or number of members in a multicast group. A host can be a member of more than one
multicast group at a time.