[rbridge] When would an RBridge say "I don't want layer 2 multicast"?

[Donald Eastlake]

On Fri, Jun 12, 2009 at 12:22 AM, Joe Touch<touch at isi.edu> wrote:
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> In the absence of this bit, there would be no way to do something in
> TRILL that isn't supported in existing L2 bridges (reportedly).

The L2 multicast registration protocols (GMRP/MMRP), as far as I can
see, allow you to register individual multicast addresses or to
register for all multicast traffic. All of the TRILL RBridge per VLAN
multicast bits (IPv4 and IPv6 derived and Other) do something that you
can't do with GMRP/MMRP in requesting huge blocks of multicast
addresses.

> If the bit were set by an operator, there's the potential for silent
> malfunction - where the operator thought there were no rbridges
> downstream, but then that changed.

I don't think any of these three bits has any effect on multicast
frames flowing downstream in a distribution tree. If an RBridge is
doing multicast pruning, these bits just make that RBridge act so as
to assure that all multicast in the three categories gets any RBridges
it is directly or indirectly feeding...

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> Joe

Thanks,
Donald