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"Classful" networking is rarely useful other than for understanding How We Got Here.

There's a handy table in the linked article which expresses each IPv4 mask length in relation to how many A, B, or C networks it is.

jermudgeon

On Mon, Dec 17, 2018 at 8:37 PM Joe <jbfixurpc@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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