Re: Joining Multicast Networks of differeing Types

From: Cisco-Engineer.com Team (ciscosurplus@gmail.com)
Date: Tue Feb 12 2008 - 18:16:05 ARST

Joe,

Thanks for the explanation, as you can see multicast is my bug bear! I need
to buck my ideas up, I find it difficult and tedious, and while I know
commands to do tasks, I guess my fundamental understanding is lacking, and
although its no likely to encounter this on the lab, I want to try to
understand.

Still not getting the static joins all the way downstream? seems very
mandrolic, whilst I appreciate dense mode is not in wide use, I can still
see the need to perform this sort of operation.

I mean if there we say 15 hops that infers a static join is required on
every hop along the way.

Back to the books for me, perhaps someone can reccomend an alternative to
developming IP multicast solutions?

thanks

Graham

On 12/02/2008, Joseph Brunner <joe@affirmedsystems.com> wrote:
>
> Urgh...
>
> Dense and sparse mode has NOTHING to do with the packets themselves...
> they
> are all still 224.0.0.0/3 DESTINATION from you guessed it a UNICAST source
> ip found in the routing table or the MROUTE table for the rpf check...
>
> The fact the interface is in sparse or dense mode means nothing to a
> multicast packet on a interface with a static join... remember, we use the
> static join to get the interface into the OIL in the absence of downstream
> pim join...
>
> When you put a static join on an interface your going to SEND a PIM join
> upstream to GET on the SOURCE TREE. Now how you get on the source tree,
> well
> that's the difference between Sparse mode and Dense mode... Sparse mode
> will
> build a shared tree to the RP, while Dense mode well, will figure things
> out...
>
> So You can just run WHATEVER mode you want until a certain point, then do
> static joins to downstream interfaces the whole way to the clients...
>
> Pim is smarter than sparse or dense mode... don't forget that...
>
> -Joe
>
> -----Original Message-----
> From: Sadiq Yakasai [mailto:sadiqtanko@gmail.com]
> Sent: Tuesday, February 12, 2008 12:32 PM
> To: Joseph Brunner
> Cc: graham@cisco-engineer.com; Graham Clarke; Cisco certification
> Subject: Re: Joining Multicast Networks of differeing Types
>
> guys,
>
> so i have been thinking about this and this is what I cant get around
> my head...did i little bit of config and still got an invalid log msg.
>
> At some point in trying to achieve what Graham is trying to do, there
> has to be a segment on which one side is running sparse mode, while
> the other is running dense mode. The two sides would ofcourse form
> neigbour relationship (tried) but forwarding of traffic is where the
> issue would come up!
>
> The side with dense mode configured wld forward traffic out the
> interface, but the side running sparse wld not accept the traffic,
> would it?
>
> Hmmm, I wonder if I correctly understood the scenario anyway?
>
> 

-- 
Thanks

Graham Clarke

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