DELL N3000 Manuale Utente

Managing IPv4 and IPv6 Multicast

• At this point, the RP no longer needs the flow of (S, G) traffic since all 

branches of the Shared Tree (in this case there is only one) have pruned off 

the flow of (S, G) traffic.

• As a result, the RP will send (S, G) Prunes back toward the source to shut 

off the flow of the now unnecessary (S, G) traffic to the RP.

• As a result of the SPT-Switchover, (S, G) traffic is now flowing only from 

the first-hop router to the last-hop router and from there to the receiver. 

Notice that traffic is no longer flowing to the RP.

The PIM standard requires support for multi-hop RP in that a router running 

PIM can act as an RP even if it is multiple router hops away from the 

multicast source. This requires that the first-hop router perform 

encapsulation of the multicast data and forward it as unicast toward the RP. 

In practice, this encapsulation is almost always performed in software due to 

the complexity of the operation. Likewise, the RP must perform de-

encapsulation and forwarding of the multicast packets in software. This 

This will occur if the RP has received an (S, G) RP-bit Prune on all 

interfaces on the Shared Tree.