IP Address starting with 253

Question

I have no idea if this is the right place to ask this question, I'm very sorry if it isn't

I have here data containing an IP address that starts with 253.45.xxx.xxx But I've looked up everywhere and I'm being told that there is no way an IP address can start with 253 (and something along the lines of 240-255.xx.xxx.xxx being reserved)

Could this be a real, valid IP address if no IP locators can find it? I don't care about what it reveals about it, I just cares that it leads somewhere or that even if it says "private" that it's still a valid IP address.

Answer 1

240/4 is what was called "Class E" address space. (the address space above "Class D", or multicast, space) It has been reserved address space for the entire existence of the internet. Because of the shear volume of systems that won't allow the use of the space, and those incorrectly treating the space as multicast, IANA/ICANN chose not to attempt to recover the address space.

It's not a "real" address. It is not routable, and it never will be.

Answer 2

It depends what you mean by "real"

240.0.0.0/4 is offically "reserved". It was never assigned to any particular use.

As such operating systems vary in how they hanle it. Windows seems to outright refuse to talk to such addresses while Linux seems quite happy to treat them as normal unicast addresses.

There have been proposals to press such addresses into service either as public internet addresses or as private addresses but it seems the outright rejection of those addresses by many deployed systems killed off those proposals http://packetlife.net/blog/2010/oct/14/ipv4-exhaustion-what-about-class-e-addresses/.

Given the current push towards IPv6 I strongly belive that the fate of such addresses is to remain forever reserved.