From: Tarun Pahuja (pahujat@gmail.com)
Date: Fri Nov 09 2007 - 13:11:26 ART
Nicky,
Switch will only get such intelligent if cgmp or igmp snooping is
enabled. igmp snooping was designed for switches that do not support cgmp.
If the switch does not have such intelligence(running either of the two), it
will simply flood the frames within the Vlan. The end hosts also need
intelligent routing(cgmp or igmp snooping) on the switch to join or leave a
multicast group.
This is a very concise answer to your questions, I am sure experts would
have more specific insight.
HTH,
Tarun
On Nov 9, 2007 11:01 AM, nicky noname <cisco2study@gmail.com> wrote:
> Hello,
>
> If you disable IGMP snooping on a switch, the switch will still
> forward IGMP messages to and from the host/ router right?
>
> 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).
>
> I have been reading about this and would like to feel sure that the
> switch will not allow hosts to join groups and receive Multicast
> traffic, if IGMP snooping is off.....but I cannot find this out for
> sure. As, but default, a switch will forward unknown multicast MAC
> addresses out all ports in the VLAN.........so I have my doubts.....
>
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