Multicast routing

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

Multicast routing

Multicast routing, the propagation of multicast listening information, is provided by multicast routing protocols such as Distance Vector Multicast Routing Protocol (DVMRP). The Windows Server 2003 family does not provide any multicast routing protocols. However, you can use the IGMP routing protocol and IGMP router mode and IGMP proxy mode to provide multicast forwarding in a single router intranet or when connecting a single router intranet to the Internet.

Single-router intranets

For an intranet that connects multiple networks by using a single router, you can enable IGMP router mode on all router interfaces to provide multicast forwarding support between multicast sources and multicast listening hosts on any network.

For more information, see Add the IGMP routing protocol and Enable IGMP router and IGMP proxy mode.

Single-router intranets and the Internet

If the server running Routing and Remote Access is attached to the MBone (the multicast-capable portion of the Internet) through an Internet service provider (ISP), you can use IGMP proxy mode to send and receive multicast traffic to and from the Internet.

In the following illustration, IGMP proxy mode is enabled on the Internet interface and IGMP router mode is enabled on the intranet interface. Multicast hosts register themselves locally and the IGMP proxy mode interface registers their memberships to the multicast-capable router at the ISP. Multicast traffic from the Internet is forwarded to the ISP router. The ISP router forwards the multicast traffic to the server running Routing and Remote Access, which then forwards the traffic to listening hosts on your intranet.

When multicast traffic is sent by an intranet host, it is forwarded over the IGMP proxy mode interface to the ISP router. The ISP router then forwards it to the appropriate downstream router. In this way, Internet hosts can receive multicast traffic sent by intranet hosts.

For more information, see Add the IGMP routing protocol and Enable IGMP router and IGMP proxy mode.

Note

• The IGMP routing protocol that uses IGMP router mode and IGMP proxy mode is not the equivalent of a multicast routing protocol. A multicast routing protocol is required for multicast forwarding and routing support in a multiple-router intranet. You may configure the IGMP router mode and IGMP proxy mode interfaces to provide multicast forwarding support in multiple-router intranets. However, it is not recommended or supported.