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We know Multicasting is defined as a single source sending to multiple recipients on a network when the receiver broadcasts a signal for acceptance. Multicasting has its own Class D IP addressing scheme, controlled and assigned by the Internet Assigned Numbers Authority (IANA). This means that all IP multicasts are in the range of 224.0.0.0 to 239.255.255.255.

I have read many website, YouTube to understand Class D IP address.

Different places I have found different answers like someone saying these addresses use for group communication that is all the host within group share the same groups IP address.

And someone saying all members of group taking different addresses with this range 224.0.0.0 to 239.255.255.255 to to make one group.

I have been finding to understand this but got nothing. Please anyone help. Which one is right from above confusing concept?

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A multicast group is a destination address (cannot be used as a source address). A host wanting to receive traffic sent to the multicast group will subscribe to the multicast group to which the traffic is sent.

One multicast address (we no longer using the Class designation) is one multicast group. Multicast addresses do not get assigned to host interfaces. Applications on hosts subscribe to a multicast group, and any traffic for any subscribed groups on a host will be passed up through the network stack to the subscribing applications. Traffic received for any group not subscribed on a host will be dropped by the host, probably at the interface for modern network interfaces.

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  • Comments are not for extended discussion; this conversation has been moved to chat.
    – Ron Maupin
    Sep 9 at 16:42
  • multicast address isn't is used as souce address, so how any multicast video are sent to subscribe users who using multicast address? My answer is suppose I am admin of multicast group, when play any video automatically remaining members got the video. But any nonadmin play any video automatically remaining gets video with admin? Am I correct?
    – Alok Maity
    Nov 9 at 4:58
  • A multicast server just starts sending to a multicast destination address. Hosts running applications for that traffic will subscribe to the multicast group so that the network interface will let in the multicast traffic and send it up the network stack to the interested application. The application can unsubscribe and the network interface will again block the multicast group traffic. Multicast is a huge subject of entire books, and involves things like IGMP and PIM, but that is the way it works in general on the same network.
    – Ron Maupin
    Nov 9 at 13:29
  • "interested application" means subscribed members of multicast group that using same application ?
    – Alok Maity
    Nov 10 at 15:23
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Multicast is a type of network communication which is based on the concept of multicast groups. A multicast group is a group of computers (more specifically, network interfaces) interested in receiving a particular stream of data. Multicast groups does not require to be located in a local network segment. Multicast groups can be located in any different network segments connected together with routers those can forward multicast traffic. Computers can join a multicast group or leave a multicast group using a protocol called as IGMP (Internet Group Management Protocol). IGMP (Internet Group Management Protocol) is an integral part of TCP/IP protocol suite.

A multicast Class D address is used as the destination address of IPv4 multicast datagrams. So, the key point to note is that in IPv4, multicast Class D addresses identify a multicast group. A computer which is interested and request datagrams sent to a multicast address becomes part of the multicast group represented by that multicast address. A multicast group can have minimum one to maximum unlimited number of computers as its members. Multicast group memberships are dynamic, means that any computer can join or leave a multicast group at any time. A computer (more specifically, network interface) can become member of many multicast groups.

If you capture and open a multicast IPv4 datagram packet, the source IPv4 address will be the IPv4 address of the multicast server sending the packet and destination IPv4 address will be the Class D multicast address (or multicast group address).

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