<myself_rajat@yahoo.com> wrote:

> ya I did check with IGMP version(using sniffer), its V3. So host is
> sending multicast reports at 224.0.0.22. As I found this special class
> D address is ment for IGMP, does this mean that its specifying the
> address of local IGMP enabled router.

The address 224.0.0.22 goes to all multicast-enabled (IGMPv3) routers
within one hop, meaning in the same IP subnet of the host. But only one
of these routers becomes the "querier," as the RFCs explain. So IGMP
never worries about the specific address of any one router. The routers,
if multiple exist in the subnet, negotiate among themselves who gets to
be in control, and the hosts can remain as dumb as possible. Always do
the same thing, no matter what the router situation is.

> And what will happen if the local subnet it having no multicast
> enabled
> router but simple unicast-router, then how that router will behave
> after getting multicast report destined to 224.0.0.22??

You would get no IGMP queries from any router, and IGMP reports would be
dropped. You will note, for example, that Windows Media Player does not
depend on IP Multicast. It can also use unicast, TCP, HTTP, etc.

Buy the way, all of this discussion has been about edge multicast router
to multicast hosts. There is a whole other discussion about building
multicast trees between routers. There have been many schemes developed
to achieve that, but it looks like the ones in favor now are under the
Protocol Independent Multicast (PIM) banner.

Bert