Dell Force10 E1200i FTOS Version 8.4.1.5 Configuration Guide for ExaScale - Page 722

www.dell.com | support.dell.com • Using PIM hello messages, the switch learns about PIM neighbors and builds a database for the VLAN and port on which the packets are received. The PIM Snooping neighbor database is the same one used for PIM-SM. Each neighbor entry stores the physical or port-channel port on which a hello message from a neighbor is received. PIM hello messages are flooded to all VLAN member ports, except the port on which the message was received. The PIM designated router on the VLAN is learned from the snooped PIM hello packets. • A PIM-SM snooping-enabled switch will proxy the join/prune messages it receives to minimize the messages it sends upstream. The switch consumes the join/prune messages received from downstream neighbors and initiates join/prune messages towards upstream neighbors. All other PIM protocol messages are flooded to VLAN member ports. PIM join/prune messages to non-existent upstream neighbors are silently dropped. PIM-SM join/prune messages towards an upstream neighbor are sent only to the port corresponding to the upstream router in the join message. PIM (S,G,Rpt) prune and (S,G,Rpt) join messages are snooped and managed according to the PIM-SM RFC. • The switch creates and maintains a tree topology with the state of PIM neighbors in the tree information base (TIB). Each PIM snooping-enabled VLAN has its own neighbor tree in the TIB. The PIM (*,G) TIB state maintains the list of multiple upstream neighbors for joins initiated by downstream routers towards the rendezvous point (RP). The PIM (*,G,) TIB adds all other upstream neighbor ports to its Outgoing Interface list, except the port to which the join was forwarded, to trigger assert conditions. The PIM (S,G) TIB state maintains the list of multiple upstream neighbors for joins initiated by downstream routers towards the source. • If the PIM designated-router (DR) flood is not disabled (default setting; refer to Disable PIM Designated-Router Flooding): • Multicast traffic is transmitted on the egress port towards the PIM DR if the port is not the incoming interface. • Multicast traffic for an unknown group is sent on the port towards the PIM DR. When DR flooding is disabled, multicast traffic for an unknown group is dropped. • Multicast traffic for known multicast group addresses, such as Local Network Control Block and Internetwork Control Block (as defined in RFC 5771), is flooded to all VLAN member ports. • In the downstream PIM TIB, states and timers are maintained for each VLAN and member port. The downstream outgoing-interface timers for each valid (*,G) and (S,G) entry are started for each VLAN/ port and upstream neighbor combination: (port,*,G,neighbor) or (port,S,G,neighbor), where port is a downstream port and neighbor is the upstream neighbor. • A timer is removed when a timer times out or a prune message is received for a specific VLAN member port. • PIM-SM snooping does not use the unicast Real Time Monitor (RTM) to forward snooped packets. • All multicast route and router information is timed-out based on the hold-time indicated in the PIM hello and PIM-SM join/prune control packets. 722 | PIM Sparse-Mode