Configuring IGMP

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

To support IPv4 multicast applications on a single-router intranet or when connecting a single-router intranet to the Internet, you can use the Routing and Remote Access service on one or more computers running Windows Server 2003, add the IGMP routing protocol component on each server, and configure the server’s outbound interface for IGMP router mode and its inbound interface for IGMP proxy mode. If your multicast applications cross the Internet, the outbound interface is the intranet interface and the inbound interface is the Internet interface.

  • IGMP router mode on the outbound interface. In Windows Server 2003, an outbound interface running in IGMP router mode listens for IGMP Membership Report messages and tracks group membership. Enable IGMP router mode on the interfaces to listening multicast hosts. The TCP/IP protocol and the IGMP routing protocol component for interfaces running in IGMP router mode forward multicast traffic.

  • IGMP proxy mode on the inbound interface. IGMP proxy mode is designed to pass IGMP Membership Report messages within a single-router intranet or from a single-router intranet to the MBone. (As explained earlier, in a multiple-router intranet, you must install routers that use one or more multicast routing protocols.) With IGMP proxy mode enabled on the inbound interface, hosts can receive multicast traffic from multicast sources and can send multicast traffic to other hosts.

Within a single-router intranet, or when connecting a single-router intranet to the Internet, you do not need routers running multicast routing protocols. However, within a multiple-router intranet that uses multicast routers running multicast routing protocols, you can still use the Routing and Remote Access service as a multicast forwarding router on the periphery of your intranet.

RFC 1112, "Host Extensions for IP Multicasting," defines address and host extensions for IP hosts that support multicasting, and defines IGMP Version 1. RFC 2236, "Internet Group Management Protocol (IGMP), Version 2," defines IGMP Version 2. Windows Server 2003 supports IGMP Version 3, described in the Internet Draft "Internet Group Management Protocol, Version 3." Under IGMP Version 3, hosts can specify interest in receiving multicast traffic from specified sources or from all but a specific set of sources.