3com 3.01.01 Manuale Utente

C

HAPTER

 6: M

ULTICAST

 P

ROTOCOL

Figure 7   Assert Mechanism Diagram

When they detect such a case, routers need to select a unique sender by using 
the assert mechanism. Routers send Assert packets to select the best path. If 
two or more have the same priority and metric, the path with a higher IP 
address will be the upstream neighbor of the (S, G) entry. This is responsible for 
forwarding the (S, G) multicast packet.

■

Graft

When the pruned downstream node needs to be restored to the forwarding 
state, the node will send a graft packet to inform the upstream node.

Configuring PIM-DM is described in the following sections:

■

■

Basic PIM-DM configuration includes:

■

■

■

Advanced PIM-DM configuration includes:

■

■

■

■

■

■

When the router is run in the PIM-DM domain, it is best to enable PIM-DM on all 
interfaces of the non-border router.

See “Configuring Common Multicast ” on page 172.

Multicast packets forwarded 
by the upstream node

Router A

Router B

Receiver

Router C