What are the IP Addresses after 223.255.255.255 and above used for?

[jtv250764]

Hello Cisco Community

I ask this question because I am currently studying in the Skills for All section and came across a statement that made me curious about the features of Unicast communications.

The statement in  9.3.1 What Did I Learn In This Module? Unicast, Broadcast and Multicast Addressing 

Skills for All "IPv4 Unicast host addresses are in the address range of 0.0.0.0 to 223.255.255.255.". 

I noted that 223.255.255.255 - 255.255.255.254 are a lot of addresses and I don't remember hearing what this block of addresses are used for or have been talked about!

I hope someone could help me understand what type of block this is please.

[Jon Marshall · Accepted solution]

224.0.0.0 -> 239.255.255.255 is the multicast address range. 

240.0.0.0 -> 255.255.255.255 is a reserved range although it is highly unlikely it will ever be used now. 

Jon

[Karsten Iwen · Accepted solution]

Adding to Jon's statement regarding the 240/4: There have been initiatives to make them available. But that was given up, likely because it was illusory that a wide range of device would ever support it.

https://datatracker.ietf.org/doc/html/draft-wilson-class-e-02

https://datatracker.ietf.org/doc/html/draft-fuller-240space-02

[jtv250764]

Thank you Jon for your swift reply

It was just after your reply that I noticed the multicast block