[nsp] Speaking of Multicast

[Gert Doering]

Hi,

On Wed, May 19, 2004 at 06:43:05PM +0200, sthaug at nethelp.no wrote:
> > (And, as this is a cisco- mailing list - cisco catalyst L2 support for
> > multicast helper protocols sucks.  Some boxes do IGMP, some do CGMP,
> > some do both, and there is no clear logic behind which boxes support
> > what).
> 
> Isn't it the case that newer boxes (e.g. 3550) do IGMP, older boxes
> do CGMP? At least that's how I think of it.

Cat5500 always does CGMP, and with more recent supervisors, IGMP.

Cat4000 (2948G) only does CGMP.

3550 only does IGMP snooping.

So what do you do if you have a mixed network with 2948G and 3550 in it,
and want/need to have high-bandwidth routed multicast groups spanning
both switches?  You loose...

I can understand that non-L3-capables witches might not be able to do
IGMP snooping - but keeping CGMP capability in the more recent switches
would enable such networks to run CGMP across all switches, pruning
the flooding appropriately.  (Yes, CGMP sucks, but having no common 
way to keep multicast packets contained sucks *more*).

gert

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Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de