Help with understanding the show ip mroute output

dan_track · ‎07-08-2010

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

andrew.prince · ‎07-08-2010

Read the below

http://www.cisco.com/en/US/tech/tk828/technologies_tech_note09186a0080093f21.shtml

HTH>

Ganesh Hariharan · ‎07-08-2010

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 · ‎07-09-2010

Thanks for that.

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

Thanks

Dan

Jon Marshall · ‎07-09-2010

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