[c-nsp] multicast on layer 2

[Tantsura, Jeff]

Gert,

Sources do register.
First-hop router creates (S,G) state and then sends Register to RP.
Which still doesn't answer the question of Andrew :) In pure L2 multiswitch
environment multicast should work as long as sources and receivers are in
the same VLAN.

P.S. Tim - I'm still confused about following statements from the link you
sent:

The router must have Protocol-Independent Multicast (PIM) enabled on the
interface connected in the VLAN where the source and receivers are located.

Note: You do not have to enable multicast routing (using the ip
multicast-routing global configuration command) on the router if you just
want to constrain multicasts on a single VLAN and you do not intend for
multicast traffic to be forwarded to other interfaces or subnets (the router
will complain that you must enable multicast routing when you enable PIM on
the router interface but this warning can be safely ignored in this
application).
------------------------------------------------------------------------
If all I want is L2 multicast why do I need a L3 interface with PIM enabled
on it. Without IGMP snooping configured every switch should flood a
multicast frame out all ports that are in the same VLAN as source.
It's kinda stupid to ask you again but :) I'd really like to understand
logic behind it. Thanks in advance 

Jeff

-----Original Message-----
From: Gert Doering [mailto:gert at greenie.muc.de] 
Sent: 29 June 2005 15:53
To: Tantsura, Jeff
Cc: 'Andrew K Ho'; Tim Stevenson; cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] multicast on layer 2

Hi,

On Mon, Jun 27, 2005 at 04:14:42PM +0200, Tantsura, Jeff wrote:
> Presence of layer 3 interface on the same VLAN could change the picture.
> Since sources and receivers would register on it enabling PIM could help.

Sources do not register - they just send packets.  Routers attached
to the source register at the PIM RP, but this is independent of 
directly attached receivers.

gert
-- 
Gert Doering
Mobile communications ... right now writing from * Isola dei Gabbiani *