From the course: Subnetting in Your Head
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Class B addresses
- [Instructor] Obviously not every company needs to support millions of hosts. Some of them may only need to support thousands of hosts, so a rule was developed with the original system to create a Class B address. It was decided that for a Class B address, the first bit must be on, in other words it has to be a one. That gives it value. In addition, the second bit must be off, which makes it valueless. Therefore, if you were to make all of the rest of the bits in the first octet be ones and have value and then add that to the 128-bit, the highest that you could get would be to 191. So therefore Class B addresses run from 128 to 191. If an address has a first octet of 128 to 191, then it's a Class B address but only if it has the appropriate subnet mask as well. Part of the standard was that the subnet mask, the underlying signal, must be 255.255.0.0, which we can also express as a slash 16, because that's 16 ones in a row followed by sixteen zeroes. What that does is it separates the…
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