Help with understanding the show ip mroute output

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Jul 8th, 2010
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Hi,


I've been trying to find a resource on the net to describe the output of show ip mroute but I'm struggling for a complete explanation. Can someone please help

me with this, let's say I have the following output (taken from an example):


(*, 239.255.0.1), 01:55:27/00:02:59, RP 192.168.7.2, flags: SJCF
  Incoming interface: Ethernet0, RPF nbr 192.168.10.2
  Outgoing interface list:
    Ethernet1, Forward/Sparse, 01:55:27/00:02:52

(133.33.33.32, 239.255.0.1), 01:54:43/00:02:59, flags: CJT
  Incoming interface: Ethernet0, RPF nbr 192.168.10.2
  Outgoing interface list:
    Ethernet1, Forward/Sparse, 01:54:43/00:02:52

(192.168.9.1, 239.255.0.1), 01:55:30/00:03:26, flags: CFT
  Incoming interface: Ethernet1, RPF nbr 0.0.0.0
  Outgoing interface list:
    Ethernet0, Forward/Sparse, 01:55:30/00:03:12

(*, 224.0.1.40), 1d00h/00:00:00, RP 192.168.7.2, flags: SJPCL
  Incoming interface: Ethernet0, RPF nbr 192.168.10.2
  Outgoing interface list: Null

More specifically what does the RPD mean in a sparse mode environment, why are some listed as "0.0.0.0" or some have an ip address listed against RPF.

Thanks
Dan

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Ganesh Hariharan Thu, 07/08/2010 - 22:08
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Hi,


I've been trying to find a resource on the net to describe the output of show ip mroute but I'm struggling for a complete explanation. Can someone please help

me with this, let's say I have the following output (taken from an example):


(*, 239.255.0.1), 01:55:27/00:02:59, RP 192.168.7.2, flags: SJCF
  Incoming interface: Ethernet0, RPF nbr 192.168.10.2
  Outgoing interface list:
    Ethernet1, Forward/Sparse, 01:55:27/00:02:52

(133.33.33.32, 239.255.0.1), 01:54:43/00:02:59, flags: CJT
  Incoming interface: Ethernet0, RPF nbr 192.168.10.2
  Outgoing interface list:
    Ethernet1, Forward/Sparse, 01:54:43/00:02:52

(192.168.9.1, 239.255.0.1), 01:55:30/00:03:26, flags: CFT
  Incoming interface: Ethernet1, RPF nbr 0.0.0.0
  Outgoing interface list:
    Ethernet0, Forward/Sparse, 01:55:30/00:03:12

(*, 224.0.1.40), 1d00h/00:00:00, RP 192.168.7.2, flags: SJPCL
  Incoming interface: Ethernet0, RPF nbr 192.168.10.2
  Outgoing interface list: Null

More specifically what does the RPD mean in a sparse mode environment, why are some listed as "0.0.0.0" or some have an ip address listed against RPF.

Thanks
Dan


Dan,


To display the contents of the IP multicast routing table show ip mroute,check out the below link with example of show ip mroute output


http://www.cisco.com/en/US/docs/ios/12_1/switch/command/reference/xrdscmd6.html


Hope to Help !!


Ganesh.H

dan_track Fri, 07/09/2010 - 03:26
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Thanks for that.


But it still doesn't explain the RPF neighbor. Any other thoughts?


Thanks

Dan

Jon Marshall Fri, 07/09/2010 - 05:02
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Dan


When the RPF (Reverse Path Forwarding) is 0.0.0.0 it means that the source of the multicast stream is connected to this router eg.


MS1 -> R1 -> R2 -> R3 -> RS1


MS1 = multicast source, RS1 = multicast receiver, mulitcast group = 229.10.10.1


R1 would have the RPF entry of 0.0.0.0 because it is directly connected to R1.

R2 would have the RPF entry of R1 as that is the RPF to get to the source of the multicast stream.

R3 would have the RFP entry of R2.


Jon

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