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This Question is Not Answered 1 Correct Answer available (4 pts) 2 Helpful Answers available (2 pts)
9360 Views 4 Replies Latest reply: Feb 6, 2010 6:35 PM by Scott Morris - CCDE/4xCCIE/2xJNCIE RSS

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Ping Multicast Group IP address

Feb 5, 2010 7:33 AM

Paul Kim 2 posts since
Oct 18, 2009

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

  • Scott Morris - CCDE/4xCCIE/2xJNCIE 8,396 posts since
    Oct 7, 2008
    Currently Being Moderated
    1. Feb 5, 2010 8:55 PM (in response to Paul Kim)
    Re: Ping Multicast Group IP address

    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

  • Scott Morris - CCDE/4xCCIE/2xJNCIE 8,396 posts since
    Oct 7, 2008
    Currently Being Moderated
    3. Feb 6, 2010 6:34 PM (in response to Paul Kim)
    Re: Ping Multicast Group IP address

    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

  • Scott Morris - CCDE/4xCCIE/2xJNCIE 8,396 posts since
    Oct 7, 2008
    Currently Being Moderated
    4. Feb 6, 2010 6:35 PM (in response to Paul Kim)
    Re: Ping Multicast Group IP address

    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

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