Join-group on SW2 didnt work


Might be a weird question from my side..

in the multicast Lab, after configuring the  Spare-dense mode on all the devices as per the Diagram, i am not able to ping the multicast address, even after i enable the join-group cmd on the SW2 interface..

but i am able to ping the Multicast group when i enabled the join-group cmd on the R6 G0/0..

i wonder if i am missing something here to configure on sw2...pls help



  • Hi Ram

    Have you checked for RPF failures?

    That's what usually gives that situation.. Remember to check for the for the auto-rp traffic too if you're using it..



  • Hello,


    there is an error in the design of the lab. SW2 f0/6 cannot be a switchport since it is connected R6 g0/0. If you do that then there will be communication between R5 and R6 on Vlan 56.

    The workaround I did was to assign SW2 f0/6 to vlan 56 and create a SVI for vlan 68. If you enable OSPF after that, you will have full reacheability from SW2 to SW1.


    Best Regards



  • Hi Dan, thanks for your reply...

    actaully R6 is at the edge of the Multicast domain, and when i Put the R6 G0/0 into the "ip igmp join-group", i am able to ping that Multicast ip address...

    SW2 F0/6 is connected directly to the R6 G0/0, when i put the Sw2 F0/6 into the "ip igmp join-group" i am not able to ping..

    i can see the (S,G) and (*,G) records in the R6 mroute table...

    just to confirm is it something to IGMP or PIM...2. do we need to have ip multicast-routing to be enables on the SW2...coz it is acting as only client...

    3. do i need to enable pim dense mode on the SW2 f0/6 as we have igmp join cmd on it..It is going to act as only client...

    SW2 ---> interface FastEthernet0/6
     no switchport
     ip address
     ip igmp join-group
     ip igmp join-group
     no ip mroute-cache

    sh ip igmp interface on SW2

    FastEthernet0/6 is up, line protocol is up
      Internet address is
      IGMP is enabled on interface
      Current IGMP host version is 2
      Current IGMP router version is 2
      IGMP query interval is 60 seconds
      IGMP querier timeout is 120 seconds
      IGMP max query response time is 10 seconds
      Last member query count is 2
      Last member query response interval is 1000 ms
      Inbound IGMP access group is not set
      IGMP activity: 2 joins, 0 leaves
      Multicast routing is disabled on interface
      Multicast TTL threshold is 0
      Multicast groups joined by this system (number of users):

    R6 - G0/0 config:

    interface GigabitEthernet0/0
     ip address
     ip pim sparse-mode
     duplex auto
     speed auto

    (*,, 1d02h/stopped, RP, flags: SP
      Incoming interface: GigabitEthernet0/0, RPF nbr
      Outgoing interface list: Null ---- it is showing NULL...looks something wrong wiht IGMP where it is not informing Router to get the multicast.

    but when i remove the ip igmp join grou and add it then i can see the *.G outgoing interface..

    (*,, 1d02h/stopped, RP, flags: SJC
      Incoming interface: GigabitEthernet0/0, RPF nbr
      Outgoing interface list:
        GigabitEthernet0/1, Forward/Sparse-Dense, 00:01:51/00:01:08

    (,, 00:01:27/00:01:54, flags: JT
      Incoming interface: GigabitEthernet0/0, RPF nbr
      Outgoing interface list:
        GigabitEthernet0/1, Forward/Sparse-Dense, 00:01:28/00:01:31 but not able to ping..

    pls help me in understanding this


  • hi Malick,

    i connected the R6 G0/0 to the other interface and build the network ...

    this has been take care..



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