Dense Mode (*,G)

[victor.hanna]

Hi All,

Topology - PIM DM

R1->R2->R3-SW1->SW2

SW2 is simulating a igmp join to group 224.12.12.12 and I am testing reachability to the group from R1 by way of ICMP no problemo so far.

Question: What is the significance of the (*,G) entry on R2 and R3, as would this not indicate a SHARED Tree Topology ? (Output Below) Is it's purpose to enable the Graft if pruned at some point ?

R2

(*, 224.12.12.12), 00:03:48/00:02:20, RP 0.0.0.0, flags: D

  Incoming interface: Null, RPF nbr 0.0.0.0

  Outgoing interface list:

    Serial0/1, Forward/Dense, 00:03:48/00:00:00

    FastEthernet0/1, Forward/Dense, 00:03:48/00:00:00

R3

(*, 224.12.12.12), 00:04:12/00:01:47, RP 0.0.0.0, flags: D

  Incoming interface: Null, RPF nbr 0.0.0.0

  Outgoing interface list:

    FastEthernet0/0, Forward/Dense, 00:04:12/00:00:00

    Serial0/1, Forward/Dense, 00:04:12/00:00:00

Thanks in advance.

[victor.hanna]

Furthermore, most of the literature on the subject seems to indicate that this entry is not important ?

The question then becomes, why is it there in the first place. Does it hold some significance to the way in which PIM-DM operates at code level ?

Cheers.