Re: PIM Sparse Mode and SPT switchover

+1 great Doc mentioned in the ATC too, explained alot for me :-)

Thanks

On Fri, Jul 29, 2011 at 4:28 AM, Nasser Abraham <nasser.abraham_at_gmail.com>wrote:

> There are a few scenarios where you cannot prevent SPT switchover. Most
> likely in your case, R5 is attempting to prevent a loop.
> As Joseph mentioned, we will need to have a look at the debug ip pim
> output.
>
> This behaviour is not documented well - the best explanation I have come
> across is a blog entry by Brian McGahan:
>
> http://blog.ine.com/2011/01/14/understanding-advanced-pim-shared-tree-designs/
>
> HTH,
> Nasser.
>
> On Wed, Jul 27, 2011 at 11:59 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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Received on Fri Jul 29 2011 - 11:20:05 ART