legacy /8

Jeffrey I. Schiller jis at MIT.EDU
Fri Apr 2 18:06:17 CDT 2010

On 04/02/2010 06:38 PM, Andrew Gray wrote:
> I understand that they were A classes and assigned to large
> companies, etc. but was it just not believed there would be more than
> 126(-ish) of these entities at the time?   Or was it thought we would
> move on to larger address space before we did?  Or was it that things
> were just more free-flowing back in the day?  Why were A classes even
> created?  RFC 791 at least doesn't seem to provide much insight as to
> the 'whys'.

/8's were not given out to large companies. They were given out to
*everyone*! In the beginning there was the ARPANET and it was considered
a large network (it was certainly an expensive network!). The notion was
that there would only be a small number of "large" networks, so 8 bits
was enough to enumerate them. The original IP plan didn't have classes
of networks at all. It was 8 bits of network and 24 bits of

It was only after network numbers started to hit the early thirties that
folks realized that there needed to be more networks and the
"class-full" approach was invented.

So most of the existing class A holders just happened to be the very
early adopters (actually the original research and government
organizations that were connected to the network).


Jeffrey I. Schiller
MIT Network Manager/Security Architect
PCI Compliance Officer
Information Services and Technology
Massachusetts Institute of Technology
77 Massachusetts Avenue  Room W92-190
Cambridge, MA 02139-4307
617.253.0161 - Voice
jis at mit.edu

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