Re: PIM Sparse Mode and SPT switchover

I should re-phrase my last sentence. You you should only see S,G entries on
the RP itself and between the multicast source. You shouldn't see S,G
entries between the RP and the Designated Router for the listener.

-Yuri

On Wed, Jul 27, 2011 at 9:06 AM, Yuri Bank <yuribank_at_gmail.com> wrote:

> You need to find out what exactly SW4 is doing when the source starts
> pinging the Mcast address: Is SW4 sending out PIM-JOIN message for S,G with
> the SPT-bit set AND PIM-Prune message for S,G with the RPT-bit set?? If so,
> it is trying to switch to the Shortest Path Tree, if not, everything is
> working as intended. SW4 should continue sending PIM- JOINS with the RPT-bit
> set and nothing else) Clear the mroute tables and set the spt-threshold
> infinity BEFORE doing the test.
>
> I've noticed odd behavior with the spt-threshold command, in that once a a
> router starts using the SPT tree it wont switch back to the Shared tree
> until the mroute table clears. If things are working correctly, you will NOT
> see a S,G entry at all. Just a *,G entry.
>
> Cheers
>
> -Yuri
>
>
>
> On Wed, Jul 27, 2011 at 3:52 AM, Shane K <shanekgs_at_gmail.com> wrote:
>
>> True! So, here is what I did in an effort to understand.
>> I've done some reading on this... and I know this is something to do with
>> there being only one path but what I want to know is WHY.
>>
>>
>> Build the shared tree from destination to RP
>>
>> SW4 - IGMP join coming in on VLAN10:
>> 3d21h: IGMP(0): Send v2 Report for 224.10.10.10 on Vlan10
>> 3d21h: IGMP(0): Received v2 Report on Vlan10 from 155.1.10.10 for
>> 224.10.10.10
>> 3d21h: IGMP(0): Received Group record for group 224.10.10.10, mode 2 from
>> 155.1.10.10 for 0 sources
>> 3d21h: IGMP(0): Updating EXCLUDE group timer for 224.10.10.10
>> 3d21h: IGMP(0): MRT Add/Update Vlan10 for (*,224.10.10.10) by 0
>>
>>
>> SW2 - received the PIM join message from SW4:
>> *Mar 4 21:36:13.234: PIM(0): Received v2 Join/Prune on Port-channel1 from
>> 155.1.108.10, to us
>> *Mar 4 21:36:13.234: PIM(0): Join-list: (*, 224.10.10.10), RPT-bit set,
>> WC-bit set, S-bit set
>> *Mar 4 21:36:13.234: PIM(0): Update Port-channel1/155.1.108.10 to (*,
>> 224.10.10.10), Forward state, by PIM *G Join
>> *Mar 4 21:36:18.359: PIM(0): Received RP-Reachable on Vlan58 from
>> 150.1.5.5
>> *Mar 4 21:36:18.359: PIM(0): Received RP-Reachable on Vlan58 from
>> 150.1.5.5
>>
>>
>> PIM Join forwarded Upstream to R5 from SW2:
>> *Jul 27 09:07:36.372: PIM(0): Received v2 Join/Prune on FastEthernet0/0
>> from
>> 155.1.58.8, to us
>> *Jul 27 09:07:36.372: PIM(0): Join-list: (*, 224.10.10.10), RPT-bit set,
>> WC-bit set, S-bit set
>> *Jul 27 09:07:36.372: PIM(0): Update FastEthernet0/0/155.1.58.8 to (*,
>> 224.10.10.10), Forward state, by PIM *G Join
>> *Jul 27 09:07:37.556: PIM(0): Send RP-reachability for 224.10.10.10 on
>> FastEthernet0/0
>>
>>
>> Now SW4, SW2 and R5 should all have *,G (Confirmed).
>>
>> R5:
>> (*, 224.10.10.10), 00:04:37/00:02:50, RP 150.1.5.5, flags: S
>> Incoming interface: Null, RPF nbr 0.0.0.0
>> Outgoing interface list:
>> FastEthernet0/0, Forward/Sparse, 00:04:12/00:02:50
>>
>> SW2:
>> (*, 224.10.10.10), 00:04:58/00:02:53, RP 150.1.5.5, flags: S
>> Incoming interface: Vlan58, RPF nbr 155.1.58.5
>> Outgoing interface list:
>> Port-channel1, Forward/Sparse, 00:04:33/00:02:53
>> SW4:
>> (*, 224.10.10.10), 00:05:14/00:02:27, RP 150.1.5.5, flags: SCL
>> Incoming interface: Port-channel1, RPF nbr 155.1.108.8
>> Outgoing interface list:
>> Vlan10, Forward/Sparse, 00:04:49/00:02:27, H
>>
>>
>> R6 will start pinging 224.10.10.10, R4 will send a PIM register message
>> (as
>> the DR) to the RP (R5).
>> R5 will acknowledge this by sending a PIM register stop back to R4.
>>
>> R5:
>>
>> *Jul 27 09:12:37.944: PIM(0): Received v2 Register on Serial0/1/0 from
>> 155.1.146.6
>> *Jul 27 09:12:37.944: PIM(0): Send v2 Register-Stop to 155.1.146.6 for
>> 0.0.0.0, group 0.0.0.0
>>
>>
>> At this stage we should see that R6, R4 and R5 will have *,G and S,G
>> entries
>>
>> R6:
>> (*, 224.10.10.10), 00:06:20/stopped, RP 150.1.5.5, flags: SPF
>> Incoming interface: FastEthernet0/0.146, RPF nbr 155.1.146.4
>> Outgoing interface list: Null
>>
>> (155.1.146.6, 224.10.10.10), 00:06:20/00:02:48, flags: PFT
>> Incoming interface: FastEthernet0/0.146, RPF nbr 0.0.0.0, Registering
>> Outgoing interface list: Null
>>
>> R4:
>>
>> (*, 224.10.10.10), 00:06:50/stopped, RP 150.1.5.5, flags: S
>> Incoming interface: Serial0/1/0, RPF nbr 155.1.45.5
>> Outgoing interface list:
>> FastEthernet0/1, Forward/Dense, 00:06:50/00:00:00
>>
>> (155.1.146.6, 224.10.10.10), 00:06:50/00:02:50, flags: T
>> Incoming interface: FastEthernet0/1, RPF nbr 155.1.146.6
>> Outgoing interface list:
>> Serial0/1/0, Forward/Sparse, 00:06:51/00:02:33
>>
>>
>>
>>
>> R5:
>>
>>
>> (*, 224.10.10.10), 00:13:52/00:03:16, RP 150.1.5.5, flags: S
>> Incoming interface: Null, RPF nbr 0.0.0.0
>> Outgoing interface list:
>> FastEthernet0/0, Forward/Sparse, 00:13:27/00:02:31
>> Serial0/1/0, Forward/Sparse, 00:06:09/00:03:16
>>
>> (155.1.146.6, 224.10.10.10), 00:07:07/00:02:34, flags: T
>> Incoming interface: Serial0/1/0, RPF nbr 155.1.45.4
>> Outgoing interface list:
>> FastEthernet0/0, Forward/Sparse, 00:07:07/00:03:21
>>
>>
>>
>>
>>
>> Now configure ip pim spt-threshold infinity on SW4 but there is no change.
>> I'm not seeing anything specific in the logs.
>>
>>
>>
>>
>>
>>
>>
>>
>> Cheers,
>>
>> S
>>
>>
>>
>>
>>
>>
>>
>>
>> On Wed, Jul 27, 2011 at 2:59 AM, Joseph L. Brunner
>> <joe_at_affirmedsystems.com>wrote:
>>
>> > Shane,
>> >
>> > No one here can give you a better answer than the router itself.
>> >
>> > What was the result of running debug ip pim on R5?
>> >
>> > I'm willing to be in plain English (ok, ciscoese) the RP will let you
>> know
>> > the before and after condition.
>> >
>> > (Hint: how many paths do you have in this network for multicast traffic
>> to
>> > flow down)
>> >
>> > -Joe
>> >
>> > -----Original Message-----
>> > From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
>> > Shane K
>> > Sent: Tuesday, July 26, 2011 4:36 PM
>> > To: Cisco certification
>> > Subject: PIM Sparse Mode and SPT switchover
>> >
>> > Hey guys,
>> >
>> > I'm having difficulty understanding this, here is the basic topology -
>> >
>> >
>> > R6-------R4 -----R5------SW2-------SW4
>> >
>> >
>> >
>> > R5 is configured as the RP, SW4 has joined the multicast group
>> > 224.10.10.10.
>> > I am pinging 224.10.10.10 from R6 and I am expecting to see *,G and S,G
>> > entries on the RP (which I do).
>> >
>> > However, on R1 and R2 I am seeing port *,G and S,G entries.
>> > I have configured *ip pim spt-threshold infinity* on SW4 to prevent the
>> SPT
>> > switchover, cleared the mroutes and started a ping from R6 again - still
>> I
>> > get the same results.
>> >
>> >
>> >
>> > R5:
>> > Rack1R5#show 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,
>> > V - RD & Vector, v - Vector
>> > Outgoing interface flags: H - Hardware switched, A - Assert winner
>> > Timers: Uptime/Expires
>> > Interface state: Interface, Next-Hop or VCD, State/Mode
>> >
>> > (*, 224.10.10.10), 00:07:18/00:03:08, RP 150.1.5.5, flags: S
>> > Incoming interface: Null, RPF nbr 0.0.0.0
>> > Outgoing interface list:
>> > FastEthernet0/0, Forward/Sparse, 00:07:18/00:03:08
>> > Serial0/1/0, Forward/Sparse, 00:05:55/00:02:31
>> >
>> > (155.1.146.6, 224.10.10.10), 00:06:54/00:03:20, flags: T
>> > Incoming interface: Serial0/1/0, RPF nbr 155.1.45.4
>> > Outgoing interface list:
>> > FastEthernet0/0, Forward/Sparse, 00:06:54/00:03:08
>> >
>> > (*, 224.0.1.40), 00:08:13/00:03:27, RP 150.1.5.5, flags: SJCL
>> > Incoming interface: Null, RPF nbr 0.0.0.0
>> > Outgoing interface list:
>> > FastEthernet0/0, Forward/Sparse, 00:08:07/00:03:19
>> > Serial0/1/0, Forward/Sparse, 00:06:57/00:03:27
>> >
>> > Rack1R5#
>> >
>> >
>> >
>> >
>> >
>> > SW2 Output:
>> > 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
>> > V - RD & Vector, v - Vector
>> > Outgoing interface flags: H - Hardware switched, A - Assert winner
>> > Timers: Uptime/Expires
>> > Interface state: Interface, Next-Hop or VCD, State/Mode
>> >
>> > (*, 224.10.10.10), 00:08:02/00:03:18, RP 150.1.5.5, flags: S
>> > Incoming interface: Vlan58, RPF nbr 155.1.58.5
>> > Outgoing interface list:
>> > Port-channel1, Forward/Sparse, 00:08:02/00:03:18
>> >
>> > (155.1.146.6, 224.10.10.10), 00:07:38/00:03:22, flags: T
>> > Incoming interface: Vlan58, RPF nbr 155.1.58.5
>> > Outgoing interface list:
>> > Port-channel1, Forward/Sparse, 00:07:38/00:03:18
>> >
>> > (*, 224.0.1.40), 00:08:52/00:03:19, RP 150.1.5.5, flags: SJCL
>> > Incoming interface: Vlan58, RPF nbr 155.1.58.5
>> > Outgoing interface list:
>> > Port-channel1, Forward/Sparse, 00:08:02/00:03:19
>> >
>> >
>> > SW4 output:
>> > 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
>> >
>> > (*, 224.10.10.10), 00:10:37/stopped, RP 150.1.5.5, flags: SCL
>> > Incoming interface: Port-channel1, RPF nbr 155.1.108.8
>> > Outgoing interface list:
>> > Vlan10, Forward/Sparse, 00:10:37/00:02:41, H
>> >
>> > (155.1.146.6, 224.10.10.10), 00:00:10/00:02:59, flags: LJT
>> > Incoming interface: Port-channel1, RPF nbr 155.1.108.8
>> > Outgoing interface list:
>> > Vlan10, Forward/Sparse, 00:00:10/00:02:49, H
>> >
>> > (*, 224.0.1.40), 00:10:37/00:02:50, RP 150.1.5.5, flags: SPCL
>> > Incoming interface: Port-channel1, RPF nbr 155.1.108.8
>> > Outgoing interface list: Null
>> >
>> > Rack1SW4#
>> >
>> >
>> >
>> >
>> > SW4 config -
>> > ip pim spt-threshold infinity
>> >
>> > interface vl25
>> > ip igmp join 224.10.10.10
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> > Any suggestions?
>> > Maybe I'm misunderstanding something here?
>> >
>> >
>> >
>> > Thanks
>> >
>> >
>> > Blogs and organic groups at http://www.ccie.net
>> >
>> > _______________________________________________________________________
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>>
>>
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Received on Wed Jul 27 2011 - 16:17:07 ART