From the course: Subnetting in Your Head
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Class A addresses
- [Instructor] To create networks that would support millions of hosts, the designers of the internet and of IP addressing devised the Class A Address. In the Class A Address, the first bit is always set to zero, that means that if you were to total the values of all of the rest of the bits, the highest that you could possibly get in that first octet with the first bit set to zero would be 127, but they said 127 is not allowed either, as part of the standard, the designers set aside 127 dot anything for their own network diagnostic purposes. So what does that do for us? Well as far as the number of networks, two to the power of seven for the seven bits in the first octet would give us 128 networks, however, we're not going to use the zero because that means that nothing came on at any time. And we're not going to use the 127 because that's part of the standard that is network diagnostic. So that leaves 126 networks. Now, it's only a Class A Address though, if the subnet mask is…
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