[cisco-voip] Multicast on 3560's

[Andre Beck]

On Tue, Dec 05, 2006 at 08:15:32AM -0800, Voll, Scott wrote:
> Is multicast on 3560s on or off by default?

Others already explained that L2 multicast within the broadcast domain
will of course work, L3 multicast (aka IP multicast routing) requires
the obvious changes (which is normal, as the boxes are supplied with
even normal ip routing defaulting to off, so there's no sense in having
ip multicast-routing defaulting to on, and no IOS platform ever did).

What's probably to add here is that IGMP snooping is on by default.
This should, however, not make any difference. In the naked L2 case,
it will behave transparent (flood all IP mcast within the BD) until
it finds a querier (IP mcast router that faces into the BD). It will
then learn using the IGMP interactions triggered by this querier. If
no IP mcast router is present, one can make the switch itself the
querier - nice to prevent unnecessary IP mcast flooding in a pure L2
environment without actual IP multicast routing.

HTH,
Andre.
-- 
                  The _S_anta _C_laus _O_peration
  or "how to turn a complete illusion into a neverending money source"

-> Andre Beck    +++ ABP-RIPE +++    IBH Prof. Dr. Horn GmbH, Dresden <-