IP Multicast Routing Protocol Basics
IP Multicast Routing is the routing of the multicast traffic. The nature of IP Multicast data is such that it has its own particular Cisco network routing challenges. There are four main Multicast protocols that are supported by the current Cisco IOS. The illustration shows you approximately where the protocols are used; the following is a list of the protocols:
Internet Group Message Protocol (IGMP): Used to track devices on LANs that are members of multicast groups (or addresses). This protocol is used between the device and the network router.
Protocol Independent Multicast (PIM): Used to track which multicast addresses or packets need to be sent to devices on the attached network segments or to other routers that are directly attached via network segments.
Distance Vector Multicast Routing Protocol (DVMRP): Used to communicate with Internet-based devices on the Multicast Backbone (MBONE). Cisco supports communication between PIM and DVMRP. At this time, most service providers do not support multicast traffic over their networks.
Cisco Group Management Protocol (CGMP): A proprietary Cisco protocol used to communicate with Cisco Catalyst switches in operations that are similar to IGMP.