Stupid Question maybe?

Tue Dec 18 06:15:26 UTC 2018

Class A,B,C represent the position of the first 0 bit in the address and a corresponding natural netmask. A=1st bit (/8), B=2nd bit (10xxxxxx, /16), and C=3rd bit (110xxxxx, /24). 

The confusion you seem to be experiencing related to the number of A,B, and C networks defined in RFC-1918 (private address space). 

In this case, a ingle A (10.0.0.0/8), 16 Bs (172.16.0.0/12), and 256 Cs (192.168.0.0/16) were set aside for private networks. 

Later, an additional block was reserved for CGNAT intermediary space (100.64.0.0/10 IIRC). 

Owen

> On Dec 17, 2018, at 21:36, Joe <jbfixurpc at gmail.com> wrote:
> 
> 
> Apologizes in advance for a simple question. I am finding conflicting definitions of Class networks. I was always under the impression that a class "A" network was a /8 a class "B" network was a /16 and a class "C" network was a /24. Recently, I was made aware that a class "A" was indeed a /8 and a class "B" was actually a /12 (172.16/172.31.255.255) while a class "C" is actually a /16. 
> 
> Is this different depending on the IP segment, i.e. if it is part of a RC1918 group it is classed differently (maybe a course I missed?) Or aren't all IP's classed the same.
> I was always under the impression, /8 = A, /16 = B, /24=C, so rightly, or wrongly I've always seen 10.x.x.x as "A", and 192.168.x.x as "B", with 172.16/12 as one that just a VLSM between the two.
> 
> Again, apologizes for the simple question, just can't seem to find a solid answer.
> 
> Happy holidays all the same!
> -Joe
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