Cisco XR 12000 Series Configuration Guide

Implementing Multicast Routing on Cisco IOS XR Software Cisco ASR 9000 Series Routers
Information About Implementing Multicast Routing
MCC-4
Multicast Configuration Guide
OL-
Multicast Routing Functional Overview
Traditional IP communication allows a host to send packets to a single host (unicast transmission) or to
all hosts (broadcast transmission). Multicast provides a third scheme, allowing a host to send a single
data stream to a subset of all hosts (group transmission) at about the same time. IP hosts 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 IP 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 group 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.
How active a multicast group is and what members it has can vary from group to group and from time
to time. A multicast group can be active for a long time, or it may be very short-lived. Membership in a
group can change constantly. A group that has members may have no activity.
Routers use the Internet Group Management Protocol (IGMP) (IPv4) and Multicast Listener Discovery
(MLD) (IPv6) to learn whether members of a group are present on their directly attached subnets. Hosts
join multicast groups by sending IGMP or MLD report messages.
Many multimedia applications involve multiple participants. Multicast is naturally suitable for this
communication paradigm.
Cisco IOS XR Multicast Routing Implementation
Cisco IOS XR software supports the following protocols to implement multicast routing:
• IGMP and MLD are used (depending on the IP protocol) between hosts on a LAN and the routers
on that LAN to track the multicast groups of which hosts are members.
• Protocol Independent Multicast in sparse mode (PIM-SM) is used between routers so that they can
track which multicast packets to forward to each other and to their directly connected LANs.
• Protocol Independent Multicast in Source-Specific Multicast (PIM-SSM) is similar to PIM-SM with
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.
• PIM-SSM is made possible by IGMPv3 and MLDv2. Hosts can now indicate interest in specific
sources using IGMPv3 and MLDv2. SSM does not require a rendezvous point (RP) to operate.
Figure 1 shows IGMP/MLD and PIM-SM operating in a multicast environment.
2. Protocol Independent Multicast in Source-Specific Multicast
3. Protocol Independent Multicast Bidirectional
4. IPv6 support on Cisco XR 12000 Series Router only
5. PIM bootstrap router
6. Multicast Source Discovery Protocol
7. Multiprotocol Border Gateway Protocol
8. Nonstop forwarding
9. Out of resource

Cisco XR 12000 Series Specifications

General

Brand	Cisco
Model	XR 12000 Series
Category	Network Router
Language	English