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 <jbfixu...@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
