PIM Dense Mode &

Unanswered Question
Jun 11th, 2009
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I have a pure dense mode network without any active senders/receivers.


this I have the following in the mroute table (on all routers).

(*,, 01:55:45/00:02:27, RP, flags: DCL

B Incoming interface: Null, RPF nbr

B Outgoing interface list:

B B B Ethernet0/0, Forward/Dense, 01:55:15/00:00:00

B B B Ethernet0/1, Forward/Dense, 01:55:40/00:00:00

B B B Serial0/0.1, Forward/Dense, 01:55:45/00:00:00

Is this normal?

Thank you!



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Overall Rating: 5 (1 ratings)
Harold Ritter Fri, 06/12/2009 - 03:32
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Hi Vladislav,

This is indeed normal behavior. All cisco routers subscribe to the multicast group address automatically when configured for multicast. This group address is used to get RP information from the mapping agent(s).


shivlu jain Mon, 06/15/2009 - 05:42
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Hi Vasilev and 39 is being used by auto-rp. This only comes when you configure ip pim sparse-dense mode.


shivlu jain

Harold Ritter Mon, 06/15/2009 - 05:57
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In fact, you will have the entry in the multicast routing table regardless whether sparse-mode, dense-mode or sparse-dense-mode is configured.


Hemant Kumar Mon, 12/24/2012 - 10:49
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Yes..This is a normal behaviour.This is because of autoRP which  is on by default


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