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I was wondering, does it make any sense to summarize(supernet) multicast IPv4 addresses ? Can anyone please explain why yes, or no ?

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    The term supernet doesn't make much sense with multicast since each group is an individual address (/32). You can summarize multiple groups in routers where you use multicast routing (very different than unicast routing). For example, there are commands in Cisco multicast where you can either use individual multicast groups, or you can use a range by summarizing.
    – Ron Maupin
    Jan 20, 2018 at 17:42
  • But if I want to send something from a network three hops away from that multicast group(and where that group is there are more multicast groups also), does it make sense then ? For example, on the first router, i put the summarized address and next hop to the second router, and so on.. , and the last router then decides which group will receive the frame .Thank you for your comment. @RonMaupin Jan 21, 2018 at 17:01
  • Multicast routing is very different than unicast routing. Multicast groups are individual addresses, not networks. Multicast routing is difficult because it must strive to not send traffic where is has not been requested. It starts with IGMP between a host wanting traffic and a multicast router, and there is PIM between multicast routers. The subject is really too broad to deal with here.
    – Ron Maupin
    Jan 21, 2018 at 17:05

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I think it always makes sense to summarize or supernet your IP addresses.

Supernetting is also known as CIDR (classless interdomain routing) as defined by RFCs 1517, 1518, 1519, and 1520. In IPv4, CIDR is one way of attempting to manage the shortage of TCP/IP addresses until IPv6 takes over.

ISPs frequently use supernetting to allocate IP addresses most effectively. There may be scenarios where you have many LANS, WLANs, or VLANs that might be optimally suited for supernetting to best administer your network needs. Keep in mind that supernetting introduces complexity to network administration that needs thorough planning, testing, documentation, and administrator competence.

Most new routing equipment and current operating systems support CIDR in their implementation of the TCP/IP protocol. However, before a supernetting implementation, it is critical to ensure that all components of your network are supernetting-aware. This includes operating systems, network services, routers, routing protocols (RIP2, for example does not support CIDR), and any network-based services used on your network.

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  • Thank you for Your answer. I was confused, because i found here cisco.com/c/dam/en/us/support/docs/ip/ip-multicast/ipmlt_wp.pdf , and I quote "Because any multicast source can send to any group address and any multicast client can receive any group without regard to geography, aggregation and summarization of multicast group addresses are meaningless" , so can you please comment that quote ? Thank you very much Jan 20, 2018 at 13:59
  • Well the guide also states: "• Internal policies on the control and deployment of network applications—Depending on the network topology, certain constrains and protection mechanisms may need to be put in place to protect network resources. A well summarized address range can help to simplify this process." - This would be a good idea if your locations span wide and you need to control which sites are allowed to connect to the streams.
    – user36472
    Jan 20, 2018 at 14:14

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