1-11 PIM ConfigurationWhen configuring PIM, go to these sections for information you are interested in:z PIM Overviewz Configuring PIM-DMz Configuring PIM-SMz Configuring PIM-SSMz Configuring PIM Common Featuresz Displaying and Maintaining PIMz PIM Configuration Examplesz Troubleshooting PIM ConfigurationThe term “router” in this document refers to a router in a generic sense or a Layer 3 switch running thePIM protocol.PIM OverviewProtocol Independent Multicast (PIM) provides IP multicast forwarding by leveraging static routes orunicast routing tables generated by any unicast routing protocol, such as routing information protocol(RIP), open shortest path first (OSPF), intermediate system to intermediate system (IS-IS), or bordergateway protocol (BGP). Independent of the unicast routing protocols running on the device, multicastrouting can be implemented as long as the corresponding multicast routing entries are created throughunicast routes. PIM uses the reverse path forwarding (RPF) mechanism to implement multicastforwarding. When a multicast packet arrives on an interface of the device, it is subject to an RPF check.If the RPF check succeeds, the device creates the corresponding routing entry and forwards the packet;if the RPF check fails, the device discards the packet. For more information about RPF, refer toMulticast Routing and Forwarding Configuration in the IP Multicast Volume.Based on the implementation mechanism, PIM falls into two modes:z Protocol Independent Multicast–Dense Mode (PIM-DM), andz Protocol Independent Multicast–Sparse Mode (PIM-SM).
