Re: multicast works even if interface is out of route table

debugging ip pim and joining the group 224.1.1.1 on R1 I see this

on R2:

Add FastEthernet0/0/10.0.12.1 to (*, 224.1.1.1), Forward state, by PIM *G
Join
Add FastEthernet0/0/10.0.12.1 to (*, 224.0.1.40), Forward state, by PIM *G
Join
Update FastEthernet0/0/10.0.12.1 to (*, 224.1.1.1), Forward state, by PIM
*G Join

on R3:

Add FastEthernet0/1/10.0.23.2 to (*, 224.1.1.1), Forward state, by PIM *G
Join

therefore I can see that the join comes to R2 using the reachable interface
fa0/0 (10.0.12.1= and not the loopback.
Then R3 (the RP) gets the join by pim from reachable interface of R2
(10.0.23.2).

Thanks Briand for your help.
I hope I can join one of your bootcamps one day! I've read very good
feedbacks from last one in UK!

On Tue, Nov 6, 2012 at 7:01 AM, Brian Dennis <bdennis_at_ine.com> wrote:

> > You mean that the join gets to the RP using the reachable interface
> instead?
>
> In regards to the statement above. How does the information about the
> multicast receiver (ip igmp join-group on R1 Loopback0) get to the RP (R3)?
> Answer this and you'll have answered your own question.
>
> --
> Brian Dennis, CCIEx5 #2210 (R&S/ISP-Dial/Security/SP/Voice)
> bdennis_at_ine.com
>
> INE, Inc.
> http://www.INE.com <http://www.ine.com/>
>
> From: ccie99999 <ccie99999_at_gmail.com>
> Date: Monday, November 5, 2012 10:50 PM
> To: Brian Dennis <bdennis_at_ine.com>
> Cc: Cisco certification <ccielab_at_groupstudy.com>
> Subject: Re: multicast works even if interface is out of route table
>
> Hi Brian,
>
> but from R3 or R2 I 'm not able to reach 1.1.1.1 (R1's l 0 )
> you mean that that router can join a group from every interface despite
> that interface is not on routing table?
> You mean that the join gets to the RP using the reachable interface
> instead?
> Actually this makes a bit more sense to me now..
>
>
>
> On Tue, Nov 6, 2012 at 6:27 AM, Brian Dennis <bdennis_at_ine.com> wrote:
>
>> Why is it not possible?
>>
>> --
>> Brian Dennis, CCIEx5 #2210 (R&S/ISP-Dial/Security/SP/Voice)
>> bdennis_at_ine.com
>>
>> INE, Inc.
>> http://www.INE.com
>>
>>
>>
>>
>>
>> On 11/5/12 9:14 PM, "ccie99999" <ccie99999_at_gmail.com> wrote:
>>
>> >Hello everybody.
>> >
>> >I'm a bit confused about this:
>> >
>> >I'm testing a minilab:
>> >
>> >*R1* - 10.0.12.0/24 - *R2* - 10.0.23.0/24 - *R3*
>> >
>> >R1 is the receiver (ip igmp join 224.1.1.1 on loo 0)
>> >R2 is the server (ping 224.1.1.1 rep 100)
>> >R3 is the autorp
>> >ospf is the igp
>> >
>> >ok, everything works.
>> >if I shutdown the R1 L0 interface the ping stop to reply. OK, fine.
>> >but if the R1 L0 is up but not configured to be part of OSPF process the
>> >ping to 224.1.1.1 is still working and replies come from 10.0.12.1
>> >
>> >(already cleared ospf and ip mroute *)
>> >
>> >I don't get how this is possible.. someone can explain this?
>> >
>> >thanks
>> >
>> >
>> >
>> >--
>> >@ccie99999
>> >
>> >
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>> >
>> >
>> >
>> >
>>
>>
>
>
> --
> @ccie99999
>
>

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