Multicast: A problem about the state of the (*,G)

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Jan 18th, 2008
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A problem about the multicast routing table.

In the first mroute:

(*, 228.230.229.1), 3d03h/00:02:24

the second mroute:

(*, 224.16.32.1), 3d03h/stopped,

The first route's expires timer is 00:02:24. Why the second is in "stopped" state? In which condition, the (*,G) will enter into the "stopped" ?


The following is the multicast route table:

(*, 228.230.229.1), 3d03h/00:02:24, RP 0.0.0.0, flags: DC

Incoming interface: Null, RPF nbr 0.0.0.0

Outgoing interface list:

Vlan21, Forward/Dense, 00:33:02/00:00:00

GigabitEthernet8/1, Forward/Dense, 3d03h/00:00:00

Vlan201, Forward/Dense, 3d03h/00:00:00

Vlan25, Forward/Dense, 3d03h/00:00:00

Vlan13, Forward/Dense, 3d03h/00:00:00

GigabitEthernet9/12, Forward/Dense, 3d03h/00:00:00

GigabitEthernet9/4, Forward/Dense, 3d03h/00:00:00

GigabitEthernet9/3, Forward/Dense, 3d03h/00:00:00


(*, 224.16.32.1), 3d03h/stopped, RP 0.0.0.0, flags: DC

Incoming interface: Null, RPF nbr 0.0.0.0

Outgoing interface list:

GigabitEthernet8/1, Forward/Dense, 3d03h/00:00:00

Vlan201, Forward/Dense, 3d03h/00:00:00

Vlan21, Forward/Dense, 3d03h/00:00:00

GigabitEthernet9/12, Forward/Dense, 3d03h/00:00:00

GigabitEthernet9/4, Forward/Dense, 3d03h/00:00:00

GigabitEthernet9/3, Forward/Dense, 3d03h/00:00:00


(10.118.1.151, 224.16.32.1), 00:02:02/00:00:57, flags:

Incoming interface: GigabitEthernet9/3, RPF nbr 10.14.1.118

Outgoing interface list:

GigabitEthernet9/4, Forward/Dense, 00:02:02/00:00:00

GigabitEthernet9/12, Forward/Dense, 00:02:02/00:00:00

Vlan21, Forward/Dense, 00:02:02/00:00:00

Vlan201, Forward/Dense, 00:02:02/00:00:00

GigabitEthernet8/1, Forward/Dense, 00:02:02/00:00:00

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Edison Ortiz Fri, 01/18/2008 - 09:00
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That's a register-stop message. This behavior can occur when the receiver or RP begins to receive traffic from the source (multicast packet would use Short Path Tree on this case)


-or-


When there aren't any receivers on the device. It tells all PIM neighbors to stop sending multicast packets destined for that specific group.


In your case, it's the former, as you have a (S,G) for such group.


HTH,


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Edison.

xiaojun-he Fri, 01/18/2008 - 10:28
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Hi, Edison. Thanks for the reply.

The multicast routes work in pim dense-mode, so there will be no register-stop messages.

Edison Ortiz Sat, 01/19/2008 - 08:40
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Point.


Haven't dealt with dense in a while, I assumed it was sparse mode - (it was also right on the output, need to be more careful while reading) - my bad :)


It seems the router is sending a prune message back to the source on the listed interfaces.


If you clear the mroute table, that entry will return? I'll have to lab that up when I get some time.


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