[eli5] Why are class A subnet masks only used for really large networks?

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(even if there are a large quantity of valid hosts that go unused)

I’ve been trying to understand IP addresses and subnet masks and I watched (and understood) the majority of this video https://youtu.be/s_Ntt6eTn94. This was a question I had at the end though. Is there some sort of disadvantage of having a class A subnet?

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Anonymous 0 Comments

There are classes of address space that were originally defined/scoped using subnet masks. Nearly all routing is classless (it doesn’t care about strict class boundaries.)

To answer: because the classful host bits can be used to define subnets. For example 10.0.0.0/8 can be broken into 10.0.0.0/24 – 10.255.255.0/24. (65,536 subnets, 256 addresses per subnet.)

Originally it was about ease of allocation of various sizes of fixed netblocks to different organizations.

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