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.
All gear is Cisco Hardware.