From: nicky noname (cisco2study@gmail.com)
Date: Sat Nov 10 2007 - 07:58:59 ART
That's very helpful thanks. I want to be sure. In this situation then,
with static macs defined, if a new client comes along and requests
traffic for a new multicast group ( one other than the defines static
macs), this will be flooded throughout the vlan, right?..I believe so
( obviously providing your network supports the group).
Thanks again.
Nic
On Nov 9, 2007 6:16 PM, Tarun Pahuja <pahujat@gmail.com> wrote:
> Nicky,
> I would highly recommend you read the following link. It tells
> you exactly how IGMP Snooping works.If IGMP snooping is not enabled on the
> switch, it would not have the intelligence to read inside an IGMP packet and
> would simply flood it across the broadcast domain.
>
> http://www.cisco.com/warp/public/473/22.html#snooping_ov
>
> As Bob suggested you can disable IGMP snooping and statically map multicast
> dynamic Content-Addressable Memory (CAM) entries to avoid flooding,
> Drawbacks being that it would not be a dynamic process and the traffic would
> be send to the client even when it does not want to listen to it as the CAM
> entries would not be removed dynamically.
>
> HTH,
> Tarun
>
>
>
> On Nov 9, 2007 12:58 PM, Bob Sinclair <bob@bobsinclair.net> wrote:
>
> >
> >
> >
> >
> > nicky noname wrote:
> > > Hello,
> > >
> > > If you disable IGMP snooping on a switch, the switch will still
> > > forward IGMP messages to and from the host/ router right?
> > >
> >
> > Yup!
> >
> > > The difference being that the IGMP messages will be flooded on the
> > > vlan. So when the multicast traffic is forwarded to the LAN switch
> > > from the router, after the router recieves an IGMP join, now will the
> > > switch drop the traffic because it has no entries in the forwarding
> > > table, or will it broadcast the traffic out all ports. ( under IGMP
> > > conditions, only the IGMP traffic goes via the CPU and the pim traffic
> > > goes to the ports listed in the forwarding table).
> > >
> >
> > If you have disabled igmp snooping, then the switch will flood multicast
> > in the vlan.
> >
> > However, there is a scenario where you disable IGMP snooping for a vlan
> > and then statically associate a multicast mac-address on a particular
> > port or ports. In this circumstance the switch will forward the
> > multicast to those ports and not flood.
> >
> > Hth,
> >
> > --
> >
> >
> > Bob Sinclair CCIE 10427 CCSI 30427
> > www.netmasterclass.net
> >
> >
> >
> >
> >
> > _______________________________________________________________________
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