From: Ashok Ananda \(aananda\) (aananda@cisco.com)
Date: Sat Oct 15 2005 - 11:38:29 GMT-3
My understanding is that it should be on the router which connects to
the member device. That is because the last hop router stops switching
over to SPT when (S,G) is received by the member device.
Thanks & Regards,
Ashok M A
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
The Great Ryan
Sent: Saturday, October 15, 2005 7:59 PM
To: Carl Willias
Cc: Cisco certification
Subject: Re: Where I should place "ip pim spt-threshold " ?
Hi,
R1(ip igmp join-group)--R2(multicast source)--R3(RP)
When R2 act as multicast source, it will contact RP(R3) and then forward
to R1 i.e. R2 -> R3 -> R1 Then it will switch to SPT i.e R2 -> R1
Thus, I want to know where "ip pim spt-threshold infinity" should be
needed?
in R2 ? in R1?
Ryan
2005/10/15, Carl Willias <mandingo2073@yahoo.com>:
> I assume you mean the infinity option. the answer is that it depends.
> Your topology does not really have an spt :-). But in reality you
> would put the command on every router up to the RP. Think of it like
> this, multicast will stay on the shared tree until a router that finds
> it has a shorter path to the multicast source, this box needs to be
> told to ignore your routing table that says if has a better way to
> get the the source and keep the tree back to the RP. That router has
> to have the ip pim spt-threshold command. In essence the choice to
> stay or leave the shared tree is a router by router choice. If you
> know the point that those tree diverge you can get away with putting
> it on one box. But it is sound practice in the real world to put it
> along the whole shared tree
>
> CW
>
> ----- Original Message ----
> From: The Great Ryan <pv.ryan@gmail.com>
> To: Cisco certification <ccielab@groupstudy.com>
> Sent: Saturday, October 15, 2005 6:21:04 AM
> Subject: Where I should place "ip pim spt-threshold " ?
>
>
> Hi Group
>
> R1--R2--R3
>
> R1 is RP
> R3 is running "ip igmp join-group" on its loopback interface
>
> Where I should place "ip pim spt-threshold " such that it will never
> switch to shortest-path tree?
>
> Place this command only on R2 or all of them ?
>
> Thanks!
> Ryan
>
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