All things related to multicast

["Kevin C. Almeroth" <>]

From: Laura Grill 
<>
To: John Zwiebel 
<>,
 

Subject: Re: Configuring an RP

This is very timely information for us since we are deploying TV to the dorms
via multicast.  This is great information, but I have a few questions:

On Wed, Sep 04, 2002 at 11:38:56AM -0700, John Zwiebel wrote:
> 
[...]> 
> 
> Where are we now?
> 
> 
>   -- Auto-RP allows you to scope "service areas" within your domain.  At
>      this time, no organization has ever shown the need to do this because
>      the amount of multicast traffic isn't that great.  But the idea is
>      that you might define an RP for "manufacturing" to use the range
>      239.123/16 and another RP for "marketing" to use that same range.
>      You -can not- do this with the Bootstrap router.

I think we are doing this with BSR but maybe I"m confused.  We have an RP
for our admin groups (239/8) and use BSR to announce this.  We have an access
list that supposedly is restricting the announcement so that only 239/8's are
being announced via BSR (this is on a cisco 6509).   We have a 2nd RP for
all other groups and this is announcing itself via auto-RP.... it has an ACL
that tells it to announce 224/4 (which includes 239/8).  We were told that
this is okay because the more specific 239/8 will take precedence as the RP.
Does that sound right?

> 
> Which is "best"? 
>   Whether auto-RP or the bootstrap router is "best" has not been determined.
>   In practice, I know of -no- organization that uses more than one RP.
>   Since the shared-tree in PIMv2 has proven to be rather cumbersome to use
>   most organizations switch immediately to the SPT. 

I don't understand this last sentence.  I thought using the shared tree 
could not be avoided in PIM.  Isn't that the way it always works -- shared 
tree
until the SPT is discovered.  How does one avoid using the shared tree with 
PIM?