Cisco Systems 78-11741-02 manual Cisco IP Multicast Routing Implementation, IPC-400

Configuring IP Multicast Routing

The Cisco IP Multicast Routing Implementation

The Cisco IP Multicast Routing Implementation

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

•IGMP is used between hosts on a LAN and the routers on that LAN to track the multicast groups of which hosts are members.

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

•Distance Vector Multicast Routing Protocol (DVMRP) is used on the MBONE (the multicast backbone of the Internet). The Cisco IOS software supports PIM-to-DVMRP interaction.

•Cisco Group Management Protocol (CGMP) is used on routers connected to Catalyst switches to perform tasks similar to those performed by IGMP.

Figure 66 shows where these protocols operate within the IP multicast environment. The protocols are further described in the sections following the figure.

Figure 66 IP Multicast Routing Protocols

Catalyst 5000 switch

Host

CGMP

Host

PIM

IGMP

Internet

MBONE

DVMRP

43274

IGMP

To start implementing IP multicast routing in your campus network, you must first define who receives the multicast. IGMP 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.

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

•A host is a receiver, including routers, that sends report messages (in response to query messages) to inform the querier of a host membership.

A set of queriers and hosts that receive multicast data streams from the same source is called a multicast group. Queries and hosts use IGMP messages to join and leave multicast groups.

IP multicast traffic uses group addresses, which are Class D IP addresses. The high-order four bits of a Class D address are 1110. Therefore, host group addresses can be in the range 224.0.0.0 to 239.255.255.255.

Cisco IOS IP Configuration Guide

IPC-400