Implementing Multicast Routing on Cisco IOS XR Software Cisco ASR 9000 Series Routers
Information About Implementing Multicast Routing
MCC-5
Multicast Configuration Guide
OL-
Figure 1 Multicast Routing Protocols Supported for Cisco IOS XR Software
Internet Group Management Protocol and Multicast Listener Discovery
Cisco IOS XR software provides support for Internet Group Management Protocol (IGMP) over IPv4
and Multicast Listener Discovery (MLD) over IPv6.
IGMP and MLD provide a means for hosts to indicate which multicast traffic they are interested in and
for routers to control and limit the flow of multicast traffic throughout the network. Routers build state
by means of IGMP and MLD messages; that is, router queries and host reports.
A set of queries and hosts that receive multicast data streams from the same source is called a multicast
group. Hosts use IGMP and MLD messages to join and leave multicast groups.
Note IGMP messages use group addresses, which are Class D IP addresses. The high-order four bits of a
Class
D address are 1110. Host group addresses can be in the range 224.0.0.0 to 239.255.255.255. The
address 224.0.0.0 is guaranteed not to be assigned to any group. The address 224.0.0.1 is assigned to all
systems on a subnet. The address 224.0.0.2 is assigned to all routers on a subnet.
IGMP and MLD Versions
The following points describe IGMP versions 1, 2, and 3:
• IGMP Version 1 provides for the basic query-response mechanism that allows the multicast router
to determine which multicast groups are active and for other processes that enable hosts to join and
leave a multicast group.
• IGMP Version 2 extends IGMP allowing such features as the IGMP query timeout and the maximum
query-response time. See RFC 2236.
Router A
Source
Receiver
Router C RP
Router B
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from RP
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