Multiple multicast sources and PIM DM
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07-21-2009 07:30 AM - edited 03-06-2019 06:52 AM
Hi there,
I am seeing the following output for one of my multicast groups:
(*, 224.0.17.42), 3w2d/stopped, RP 0.0.0.0, flags: DC
Incoming interface: Null, RPF nbr 0.0.0.0
Outgoing interface list:
Vlan3462, Forward/Sparse-Dense, 3d04h/00:00:00, H
Vlan1, Forward/Sparse-Dense, 4d18h/00:00:00, H
Vlan320, Forward/Sparse-Dense, 3w2d/00:00:00, H
Vlan310, Forward/Sparse-Dense, 3w2d/00:00:00, H
Vlan300, Forward/Sparse-Dense, 3w2d/00:00:00, H
(155.195.63.178, 224.0.17.42), 00:00:31/00:02:28, flags:
Incoming interface: Null, RPF nbr 0.0.0.0
Outgoing interface list:
Vlan300, Forward/Sparse-Dense, 00:00:31/00:00:00, H
Vlan310, Forward/Sparse-Dense, 00:00:31/00:00:00, H
Vlan320, Forward/Sparse-Dense, 00:00:31/00:00:00, H
Vlan1, Forward/Sparse-Dense, 00:00:31/00:00:00, H
Vlan3462, Forward/Sparse-Dense, 00:00:31/00:00:00, H
(206.200.5.42, 224.0.17.42), 07:25:33/00:02:59, flags: T
Incoming interface: Vlan3462, RPF nbr 192.168.130.242, Mroute
Outgoing interface list:
Vlan300, Forward/Sparse-Dense, 07:25:33/00:00:00, H
Vlan310, Prune/Sparse-Dense, 00:00:30/00:02:29, H
Vlan320, Forward/Sparse-Dense, 07:25:33/00:00:00, H
Vlan1, Forward/Sparse-Dense, 07:25:33/00:00:00, H
What causes the S,G entry with no flags, no incoming interface, and no RPF?
My thinking is that since I have two sources for this group, my router is using PIM asserts to shutdown one of the sources. Is that accurate?
Regardless, would having two sources for this group, with all interfaces in dense mode, cause problems with the data?
Thanks in advance,
Brandon
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07-21-2009 08:42 AM
Hello Brandon,
each (S,G) group should be treated indipendentently.
Possible reasons for what you see is an RPF check failure for source1 155.195.63.178
you can check this with
sh ip rpf 155.195.63.178
if traffic for (S1,G) is received on an interface that is not the one that the node would use to reach S1 an RPF check failure occurs.
PIM is running in dense mode because states are timed with a timer of 3 minutes:
after 2 min 28 sec a new attempt to flood traffic for group (S1,G) will be done.
(S2,G) is
(206.200.5.42, 224.0.17.42), 07:25:33/00:02:59, flags: T
is in forwarding state since 7 hours 25 min 33 sec ago.
Hope to help
Giuseppe
PIM assert is used when two PIM multicast routers have to decide who will be responsible for sending traffic for a (S,G) in a lan segment.
PIM assert is not used for deciding which source is legitimate.
Hope to help
Giuseppe
