Multicast RPF Failure NBMA Troubleshooting


You are responsible for the frame relay and multicast configuration within the network. You use a lot of hub and spoke topologies and up to now you haven’t seen any problems. Yesterday one of your customers called claiming they are having some problems. There is a videostation behind one of the spoke routers streaming video using multicast. It seems one of the other spoke routers is unable to receive this stream…let’s see what you can do.


  • All IP addresses have been preconfigured for you as specified in the topology picture.
  • OSPF is preconfigured for full connectivity.
  • Do not use show run! (this will spoil the fun đŸ™‚ use the appropiate ‘show’ and ‘debug’ commands. This will teach you the skills needed to become a true troubleshooting master.
  • Start a ping on router SpokeA to IP address to generate multicast traffic.
  • Configure the network so router Receiver can receive this multicast traffic.
  • You are not allowed to make any changes to the frame-relay network or change the PIM mode.




Multicast RPF Failure NBMA Troubleshooting

Video Solution:

Configuration Files

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Written by René Molenaar - CCIE #41726

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About the Author: Rene Molenaar

René - CCIE #41726 is the creator of where he shares CCNA, CCNP and CCIE R&S labs. He also blogs about networking on


  1. after completing the lab, i just changed the senario to sparse mode all accross , and used "ip pim nbma mode" at the hub, however the solution is not working. (i am not using tunnels)

    Help me fix this way.


    1. Hi Shoeb,

      What exactly is working/not working and what did you try?


      1. Hi Rene,
        I configured pim sparse-mode on all the router interfaces.
        (after removing dense mode and Tunnels)

        then i used "ip pim nbma mode" on HUB router Serial interface.

        however i was unable to ping from Spoke A to receiver.


        1. Hi Shoeb,

          Did you configure a RP (Rendezvous Point)? Do all routers see the RP?


          1. ya of course.
            i configured static rp.

            it didn’t worked with any of the router acting as rp (i tried making rp as receiver, spokeB, and hub)

            1. I just tested this to see if anything funky was going on. It’s working now so let me describe what I did:

              – Make sure OSPF is working, you need to change the OSPF network type for frame-relay.
              – Enable "ip pim sparse mode" on ALL routers, including the receiver.
              – Make sure all PIM neighbors are formed.
              – Use the "ip pim rp-address" command on all routers to select the HUB as the RP.
              – Configure "ip pim nbma-mode" on the HUB.
              – Configure "ip igmp join-group" on the Receiver.

              Ping from SpokeA to the the multicast group address and it works! If you want to see my configs open a forum post and I’ll post them there ok?

              1. Yes , i have done all that same way, Unfortunately i am not getting it…

                i am able to ping from HUB , however ping from Spoke A fails…

                SpokeA#pi re 4

                Type escape sequence to abort.
                Sending 4, 100-byte ICMP Echos to, timeout is 2 seconds:
                HUB#pi re 4

                Type escape sequence to abort.
                Sending 4, 100-byte ICMP Echos to, timeout is 2 seconds:

                Reply to request 0 from, 124 ms
                Reply to request 0 from, 200 ms
                Reply to request 1 from, 100 ms
                Reply to request 1 from, 136 ms
                Reply to request 2 from, 76 ms
                Reply to request 2 from, 128 ms
                Reply to request 3 from, 80 ms
                Reply to request 3 from, 104 ms

                HUB#s ip os ne

                Neighbor ID Pri State Dead Time Address Interface
       0 FULL/DROTHER 00:01:53 Serial0/0
       0 FULL/DROTHER 00:01:53 Serial0/0
                HUB#s ip pim ne
                PIM Neighbor Table
                Neighbor Interface Uptime/Expires Ver DR
                Address Prio/Mode
       Serial0/0 00:31:32/00:01:43 v2 1 / S
       Serial0/0 00:31:32/00:01:43 v2 1 / S

                SpokeA#s ip pim ne
                PIM Neighbor Table
                Neighbor Interface Uptime/Expires Ver DR
                Address Prio/Mode
       Serial0/0 00:30:10/00:01:34 v2 10/ DR S
                PIM Group-to-RP Mappings

                Group(s):, Static
                RP: (?)

                HUB#s ip mroute

                (,, 00:02:12/00:02:57, flags: PT
                Incoming interface: Serial0/0, RPF nbr
                Outgoing interface list: Null

                HUB#sh run int Serial0/0
                Building configuration…

                Current configuration : 179 bytes
                interface Serial0/0
                ip address
                ip pim dr-priority 10
                ip pim nbma-mode
                ip pim sparse-mode
                encapsulation frame-relay
                serial restart-delay 0


                  1. its working in ospf POINT_TO_MULTIPOINT mode
                    earlier i had configured ospf NON_BROADCAST mode on FR, in which it do not work.

                    Thanks Rene.

                    1. however ideally this should not happen as it is Protocol Independent multicast.

                    2. Your multicast configuration is fine but your OSPF configuration probably has an error, there are two things to check here:

                      – The non-broadcast network type requires the election of a DR. Make sure the HUB has become the DR and not one of the spokes or you’ll have reachability issues.
                      – Check your next-hop IP addresses and see if you have all the required frame-relay mappings.

                      If you check/fix that then it will work perfectly fine with OSPF non-broadcast.

                      Keep in mind the "independent" part of PIM doesn’t mean it does not require a routing protocol. It means it’s not "dependent" on 1 routing protocol and that it can use "any" routing protocols you choose. PIM requires a routing table but doesn’t care where the information in it came from, that’s why it’s called "independent".

                    3. certainlly, i made sure that there is no error in my ospf config.

                      as u can see in above pasted serial interface config, i made sure HUB becomes DR
                      also i added frame relay map ip dlci on each spoke for the other.
                      also , to form neighbours i added explicit neighbour command for spokes on the HUB router.

                      even then the multicasting was not working.
                      you can try modifing your final config.

  2. Once again, I think adding a frame-relay map is changing the frame-relay configuration…just saying…

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