IPv4 /8 =126 networks? or 254 networks?

[gychen]

Hello,

I'm reading this article (http://www.apnic.net/__data/assets/pdf_file/0003/6492/20060421-cnnog-addressing.pdf)regarding IPv4 Addressing in China, in page 9 there's a graph showing the "IPv4 /8 Address Space Status". It listed a total of 256 networks.

AFAIK, Class A network is 8 bit network prefix, and its first bit has to be "0", thus a maximum of 126, which is (2 7 -2,) networks can be defined. So that when I read this article I thought its written wrong. Am I right?

THanks,
-Gary

[ciscodaze]

You are correct.

the first bit in the class A octet scheme is fixed...

00000000 THROUGH 01111111 (the full range, going from all bits off, to all bits on)

which is the same as saying, network 0 through network 128.

You MINUS the 0 network which you can't use, AND MINUS the 128 network which you can't use (because its really the beginning of the next class range 128 - 192), AND MINUS THE 127 loopback

that leaves your network range as 1-126, as you said or, more specifically,
1.0.0.1 - 126.255.255.254,
if you want to include the hosts too.