On Oct 5, 2017, at 4:14 PM, William Herrin <bill@herrin.us> wrote:
On Thu, Oct 5, 2017 at 1:32 PM, Jerry Cloe <jerry@jtcloe.net> wrote:
Several years ago I remember seeing a mathematical justification for it, and I remember thinking at the time it made a lot of sense, but now I can't find it.
Hi Jerry,
If there's special ASIC-friendly math here, beyond what was later generalized with CIDR, it's not obvious.
10.0: 0000 1010 0000 0000
172.16: 1010 1100 0001 0000
172.31: 1010 1100 0001 1111
192.168: 1100 0000 1010 1000
AFAIK, it was simply one range each from classes A, B and C.
As mentioned in one of the links posted earlier, 10.0.0.0/8 was the original ARPANET class A assignment. (See RFC 970, which brings back a lot of memories.) Once the ARPANET was shut down in 1990 that block was no longer used, so it became available for reuse in RFC1918. I have a vague recollection of parts of 192.168.0.0/16 being used as default addresses on early Sun systems. If that's actually true, it might explain that choice. Steve