All things related to multicast

[Toerless Eckert <>]

On Thu, Jun 27, 2002 at 08:32:44PM -0700, Nitin jain wrote:
> Hi Lucy,
> 
>    I am curious why turning off the IGMP snooping should not work in every
> case. If that doesn't work, we should examine the case as the plain layer2
> switch/hub would also exhibit the same issue. 

If you have a network with 10Mbps, the amount of unwanted multicast
traffic may be to much to bear for some host. After all, avoiding this 
is the purpose of IGMP Snooping !

> I would think that this would be the case for any vendor that is not aware
> of IGMPv3 in the snooping implementation as IGMPv2 did not care about the
> source specificness. Therefore, plain layer2 forwarding would not be
> adequate for source specific joins, or exclude source. Thus, it would be
> advisable not to turn on any Layer 2 specific snooping, be it CGMP, IGMP
> etc. if the implementation is unaware of IGMPv3.

CGMP actually works together with IGMPv3, it just doesn't constrain
unwanted traffic as well as IGMP Snooping enabled for IGMPv3 could.
See the documentation on IGMPv3 in IOS.

Cheers
        Toerless