Hello Champion
Hmm, I’m not sure I understand your question. The router doesn’t forward multicast packets to the source. It forwards multicast packets sent by the source to the intended multicast destinations based on the multicast group (multicast IP address) that is in the destination of the multicast packets. In such cases, IGMP is used by hosts to indicate that they are interested in receiving multicast traffic for that particular multicast group.
Now when it comes to the use of the 224.0.0.x series of multicast addresses, these are a specialized range of addresses (from 224.0.0.0 to 224.0.0.255) which are reserved for use by network protocols on a local network segment. See the following Cisco documentation about these addresses:
These addresses will never be routed by any routers. As stated in Rene’s post, these addresses are ignored by IGMP, and are actually treated as broadcast traffic when received by a switch.
I hope this has been helpful!
Laz