Re: all zeroes/all ones used in host IP's...

[H. Peter Anvin]

Followup to:  <[e-mail]>
By author:    Riley Williams <[e-mail]>
In newsgroup: linux.dev.kernel
> 
>  1. The relevant standard states that all IP addresses are
>     classified as one of classes A, B, C or D depending only
>     on the FIRST octet/byte thereof, as follows:
> 
> 	0		Reserved
> 	1-127		Class A		 8 bit
> 	128-191		Class B		16 bit
> 	192-223		Class C		24 bit
> 	224-254		Class D
> 	255		Reserved
> 
>     Class D appears to have some strange rules associated with it,
>     and I can't claim to fully understand them, so I will not
>     analyse it further.
> 

Actually, that is...

	224-239		Class D		Multicasting
	240-255		Class E		Experimental (reserved)

Also, network 127 is reserved for host-local addressing.

These days, the class A/B/C distinction is academic, although the
numbering authorities still assign blocks out of the A, B or C ranges
roughly depending on block size.  The cutoffs seem to be somewhere
around /10 or /11 and /16.

	-hpa
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