451239.255.0.1 7.1.1.100 Vlan4 0 2005: 1239.255.0.1 1.1.1.100 Vlan1 0 2006: 12007: 1Switch #Displayed information ExplanationName The interface list used by the multicast protocol and basicinformation for the interfaces.Index Index number for the interfaceGroup Multicast forwarding entry group addressOrigin Multicast forwarding entry source addressIif Multicast forwarding entry ingress interfaceWrong The number of multicast packets (to this forwarding entry) fromwrong incoming interfacesOif: TTL Oif stands for the outgoing interface list, this list can be referredto by the index number according to the information list above;TTL is the TTL threshold value for that outgoing interface.16.3 PIM-DM16.3.1 Introduction to PIM-DMPIM-DM (Protocol Independent Multicast Dense Mode) is a dense mode multicastprotocol. It is good for use in small networks as the multicast group members are relativelyconcentrated in such network environment.The work process of PIM-DM can be summarized as the following phases: neighbordiscovery, flooding & prune, grafting.1. Neighbor discoveryPIM-DM routers need to discover the neighbors with HELLO packets on start up. Networknodes running PIM-DM keeps contact with HELLO packets. The HELLO packets are sentin regular intervals.2. Flooding and PrunePIM-DM assumes all hosts in the network are ready for receiving multicast data. When amulticast source S starts sending data to multicast group G, the router will first performRPF check against the unicast route table to the multicast packet. If checked ok, therouter will create a (S, G) entry and forward the multicast packet to all downstreamPIM-DM nodes in the network (Flooding). If RPF check fails, indicating the multicastpacket is coming from the wrong interface, the packet will be discarded. After this process,each node in the PIM-DM multicast domain will create a (S, G) entry. If no multicast groupmember exists in the downstream nodes, then a prune message will be sent to the
