4 Replies Latest reply: Feb 6, 2010 6:35 PM by Scott Morris - CCDE/4xCCIE/2xJNCIE RSS

    Ping Multicast Group IP address

    Paul Kim

      Hi all,

       

      Can anyone explain why there is a difference between 239.255.255.253 and 239.255.255.250 in terms of ping reply?

      I am seeing no difference of 2 multicast groups's routes and any configuration.

       

      However  239.255.255.253 group members reply the ping from the very first upstream router but 239.255.255.250 members don't reply to ping request.

       

      c4500#sh ip mroute 239.255.255.253
      IP Multicast Routing Table
      Flags: D - Dense, S - Sparse, B - Bidir Group, s - SSM Group, C - Connected,
             L - Local, P - Pruned, R - RP-bit set, F - Register flag,
             T - SPT-bit set, J - Join SPT, M - MSDP created entry,
             X - Proxy Join Timer Running, A - Candidate for MSDP Advertisement,
             U - URD, I - Received Source Specific Host Report, Z - Multicast Tunnel
             Y - Joined MDT-data group, y - Sending to MDT-data group
      Outgoing interface flags: H - Hardware switched, A - Assert winner
      Timers: Uptime/Expires
      Interface state: Interface, Next-Hop or VCD, State/Mode

      (*, 239.255.255.253), 2d11h/00:02:48, RP 0.0.0.0, flags: SJC
        Incoming interface: Null, RPF nbr 0.0.0.0
        Outgoing interface list:
          Vlan2021, Forward/Sparse, 2d11h/00:02:48, H


      c4500#sh ip mroute 239.255.255.250
      IP Multicast Routing Table
      Flags: D - Dense, S - Sparse, B - Bidir Group, s - SSM Group, C - Connected,
             L - Local, P - Pruned, R - RP-bit set, F - Register flag,
             T - SPT-bit set, J - Join SPT, M - MSDP created entry,
             X - Proxy Join Timer Running, A - Candidate for MSDP Advertisement,
             U - URD, I - Received Source Specific Host Report, Z - Multicast Tunnel
             Y - Joined MDT-data group, y - Sending to MDT-data group
      Outgoing interface flags: H - Hardware switched, A - Assert winner
      Timers: Uptime/Expires
      Interface state: Interface, Next-Hop or VCD, State/Mode

      (*, 239.255.255.250), 2d11h/00:02:42, RP 0.0.0.0, flags: SJC
        Incoming interface: Null, RPF nbr 0.0.0.0
        Outgoing interface list:
          Vlan2022, Forward/Sparse, 2d11h/00:02:41, H
          Vlan2021, Forward/Sparse, 2d11h/00:02:40, H

       

      c4500#ping 239.255.255.253

      Type escape sequence to abort.
      Sending 1, 100-byte ICMP Echos to 239.255.255.253, timeout is 2 seconds:

      Reply to request 0 from alpha (10.9.66.62), 4 ms
      Reply to request 0 from beta (10.9.80.146), 4 ms
      Reply to request 0 from young  (10.9.80.61), 4 ms
      Reply to request 0 from check (10.9.80.16), 4 ms

       

       

      c4500#ping 239.255.255.250

      Type escape sequence to abort.
      Sending 1, 100-byte ICMP Echos to 239.255.255.250, timeout is 2 seconds:
      .

       

       

      Any thoughts on this, please let me know.

       

      Thanks,

      Paul

        • 1. Re: Ping Multicast Group IP address
          Scott Morris - CCDE/4xCCIE/2xJNCIE

          In order to reply to a multicast ping, you either have to be a host with multicast software running, or a router with 'igmp join-group x.x.x.x' on it.

           

          Do you have devices joined to both groups?

           

          Scott

          • 2. Re: Ping Multicast Group IP address
            Paul Kim

            Hi Scott,

             

            I have configured a router with ip igmp join-group command as you suggested but still I can't ping the group address.

             

            us-mpls-router#sh run int f0/0
            Building configuration...

            Current configuration : 199 bytes
            !
            interface FastEthernet0/0

            ip address 10.16.17.46 255.255.255.240
            ip pim sparse-mode
            ip igmp join-group 239.192.50.159 source 10.9.18.23
            duplex full
            speed 100
            end

             

            us-mpls-router#ping 239.192.50.159

            Type escape sequence to abort.
            Sending 1, 100-byte ICMP Echos to 239.192.50.159, timeout is 2 seconds:

            .

             

            us-mpls-router#sh ip mroute
            IP Multicast Routing Table
            Flags: D - Dense, S - Sparse, B - Bidir Group, s - SSM Group, C - Connected,
                   L - Local, P - Pruned, R - RP-bit set, F - Register flag,
                   T - SPT-bit set, J - Join SPT, M - MSDP created entry,
                   X - Proxy Join Timer Running, A - Candidate for MSDP Advertisement,
                   U - URD, I - Received Source Specific Host Report,
                   Z - Multicast Tunnel, z - MDT-data group sender,
                   Y - Joined MDT-data group, y - Sending to MDT-data group
            Outgoing interface flags: H - Hardware switched, A - Assert winner
            Timers: Uptime/Expires
            Interface state: Interface, Next-Hop or VCD, State/Mode

            (10.9.18.23, 239.192.50.159), 00:33:14/00:03:24, flags: sT
              Incoming interface: Multilink1, RPF nbr 159.24.251.85
              Outgoing interface list:
                FastEthernet0/0, Forward/Sparse, 00:33:14/00:03:07

             

            Also I have Windows Media Player pulling a multicast stream as well.

             

            I think I'm  missing some critical puzzle to understand the ping to the multicast group.

             

            Thanks,

            Paul
            .

            • 3. Re: Ping Multicast Group IP address
              Scott Morris - CCDE/4xCCIE/2xJNCIE

              The ones who have the "join-group" are the ones who will RESPOND to the ping.  So go do a DIFFERENT router to use the ping command! 

               

              Perspective!

               

              Scott

              • 4. Re: Ping Multicast Group IP address
                Scott Morris - CCDE/4xCCIE/2xJNCIE

                Oh yeah...  One other note...  Make sure there aren't and RPF failures along the way!  (debug ip mpacket or debug ip mrouting may help)

                 

                Scott