Defining what type of casting based on IPv4 address

Question

I'm kinda new to networking. I have a small question, how can I determine what type of casting (unicast, multicast or broadcast) is it based on IPv4 address. For example: 142.55.172.200

I tried to search up but I still don't understand. Thank you.

Answer 1

For IPv4, unicast addresses are in the 0.0.0.0 to 223.255.255.255 range*, multicast addresses are in 224.0.0.0 to 239.255.255.255 address range.

*Broadcast addresses are more complicated. There is the limited broadcast address (255.255.255.255) that works on all networks, but there is also a network broadcast address that is the last address in a network.

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For a full explanation of IPv4 network addressing, see this two-part answer.

Answer 2

• 0.0.0.0 to 223.255.255.255 are normally unicast.
• 224.0.0.0 to 239.255.255.255 are multicast
• 240.0.0.0 to 255.255.255.254 are reserved and will most likely never be allocated. Some operating systems refuse to work with them at all, others treat them as regular unicast addresses.
• 255.255.255.255 is limited broadcast. This will be broadcast to all systems on the same "link" as the sender.
• The last address of a subnet (other than a /31) is also broadcast. This can be used to broadcast to a specific subnet, either if a system is multi-homed or if the router serving that subnet allows "directed broadcasts"

Directed broadcast is nearly always disabled nowadays, since it is a useful tool for attackers.

Unfortunately there is no way to reliablly distinguish a unicast address from a broadcast one. Since subnets can vary in size and some systems may not use traditional subnets at all there is no general way to determine the "last address of a subnet".