Multicast Issue with 3560

I'm having a problem I have been unable to figure out thus far. My setup is this: (VLAN10)--SW4--SW2--R5--R4--R6. R6 is the source of an ICMP multicast stream destined for group 224.10.10.10. The RP is statically configured as R5's loopback for 224.0.0.0/24. All devices are in sparse-dense mode. SW4's VLAN10 interface is configured as the only listener for the group. I cannot get packets to show up in any debugs on SW2 unless I configure SW2's interface connected to SW4 to join the same multicast group. Even then, I still don't get ICMP responses from SW4.

 

Relevant output from R5 (RP):


Rack11R5#sh ip mroute

<snip>

(*, 224.10.10.10), 00:03:17/00:03:09, RP 150.11.5.5, flags: S

  Incoming interface: Null, RPF nbr 0.0.0.0

  Outgoing interface list:

    FastEthernet0/0, Forward/Sparse-Dense, 00:03:17/00:03:09

 

(155.11.146.6, 224.10.10.10), 00:02:52/00:00:29, flags: T

  Incoming interface: Serial0/1/0, RPF nbr 155.11.45.4

  Outgoing interface list:

    FastEthernet0/0, Forward/Sparse-Dense, 00:02:52/00:03:09

<snip>

Rack11R5#debug ip mpacket fastswitch

IP multicast fastswitch packets debugging is on

*Feb 25 17:48:01.387: FS(0): Receive s=155.11.146.6 d=224.10.10.10 id=1770 prot=1 size=104(100) ttl=253 from Serial0/1/0

*Feb 25 17:48:01.387: FS(0): Forward s=155.11.146.6 d=224.10.10.10 id=1770 prot=1 size=114(100) ttl=253 to FastEthernet0/0

 

R6:


Rack11R6#ping 224.10.10.10

 

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 224.10.10.10, timeout is 2 seconds:

.....

 

SW2:


Rack11SW2#sh ip mroute

<snip>

(*, 224.10.10.10), 00:26:56/00:03:05, RP 150.11.5.5, flags: S

  Incoming interface: Vlan58, RPF nbr 155.11.58.5

  Outgoing interface list:

    Port-channel1, Forward/Sparse-Dense, 00:26:56/00:03:05

 

(*, 224.0.1.40), 00:27:32/00:02:29, RP 150.11.5.5, flags: SJCL

  Incoming interface: Vlan58, RPF nbr 155.11.58.5

  Outgoing interface list:

    Port-channel1, Forward/Sparse-Dense, 00:27:32/00:02:56

 


Rack11SW2#debug ip mpacket fastswitch 224.10.10.10

IP multicast fastswitch packets debugging is on for group 224.10.10.10

*I get no output here*

 

Rack11SW2#sh ip cef 224.0.0.0/24

224.0.0.0/24

  receive

 

 

I already did RPF checks, but even those should show up in a debug if they were wrong. The only device between R5 and SW2 is SW1 (Layer 2 only for VLAN connectivity) and I thought this may be causing the problem, but I don't see how. Please share your suggestions. 

Comments

  • I created a tunnel interface to try to rule out any Layer 2 issues between R5 and SW2. Now I see that SW2 is forwarding the packets, even though the debug output from above still shows nothing at all. I looked at the counters and noticed that they are incrementing on the receiving side and the sending side on SW2:


    Rack11SW2#sh ip pim int po1 det

    Port-channel1 is up, line protocol is up

      Internet address is 155.11.108.8/24

      Multicast switching: fast

      Multicast packets in/out: 0/523 <-- Incrementing

      Multicast TTL threshold: 0

      PIM: enabled

        PIM version: 2, mode: sparse-dense

        PIM DR: 155.11.108.10

        PIM neighbor count: 1

        PIM Hello/Query interval: 30 seconds

        PIM Hello packets in/out: 179/178

        PIM State-Refresh processing: enabled

        PIM State-Refresh origination: disabled

        PIM NBMA mode: disabled

        PIM ATM multipoint signalling: disabled

        PIM domain border: disabled

        PIM neighbors rpf proxy capable: TRUE

      Multicast Tagswitching: disabled


    Rack11SW2#sh ip pim int tun85 det

    Tunnel85 is up, line protocol is up

      Internet address is 155.11.85.8/24

      Multicast switching: fast

      Multicast packets in/out: 434/0 <-- Incrementing

      Multicast TTL threshold: 0

      PIM: enabled

        PIM version: 2, mode: sparse-dense

        PIM DR: 0.0.0.0

        PIM neighbor count: 1

        PIM Hello/Query interval: 30 seconds

        PIM Hello packets in/out: 50/51

        PIM State-Refresh processing: enabled

        PIM State-Refresh origination: disabled

        PIM NBMA mode: disabled

        PIM ATM multipoint signalling: disabled

        PIM domain border: disabled

        PIM neighbors rpf proxy capable: TRUE

      Multicast Tagswitching: disabled

     

    Before I created the tunnel, neither of these pim interface counters (Po1 or the original VL58) were increasing on SW2. 

     

    Another oddity. I received a string of replies on R6 in one instance. The command "ip pim spt-threshold 128" was not in effect on SW4. I tried a ping from R6, and it worked. I added the spt command back into SW4 and tried to ping it again from R6, no response. I removed the command and tried to ping from R6, no response. The inconsistency appears to be only in the switches as everytime I generate a straffic stream, the (S,G) makes it all the way to the RP.

  • After more thread searching, I found this: http://ieoc.com/forums/t/7382.aspx

     

    Turns out when ip spt-threshold is configured on SW4 it breaks sparse mode. Removing the command wasn't quite enough. I had to remove it and then reload the switch and then everything started working with sparse mode. 

  • Hi

    Can you re-define your problem statement and also the solution which you figure out fot the same.?

  • Okay sometimes a reload does fix the problem that is right!

    The switches are REAL gear as you said...are the routers real too or is it emulated dynamips equipment?

     

    Regards!

    Markus

  • The problem is that the last hop leaf device (when a 3560) does not operate in sparse mode correctly when "ip spt-threshold" is configured. The "fix" is to not configure this command.

  • The switches are REAL gear as you said...are the routers real too or is it emulated dynamips equipment?

     

    All gear is Cisco Hardware.

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