Question about subnetting

[Janna1]

Hello. I'm teaching myself about subnetting. The book I'm using is saying something I don't understand, and I'm awful at math and computers in general.

start with a beginning subnet mask and extend the subnet extension until you have the number of subnets you need. The formula for determining how many subnets you create is 2 to the power of y, where y is the number of bits you add to the subnet mask.

If you move the network ID extension over one, it’s only a single digit, 2 to the power of 1.

let’s take /24 and subnet it down to /26. Extending the network ID by two digits creates four new network IDs, 2 to the power of 3 = 6.

But I see only 4 possible permutations.
00|000000 (0)
01|000000 (64)
10|000000 (128)
11|000000 (192)

Where are the other 2 subnets the formula says should exist? Moreover, the equation 2 to the power of 3 = 8. I'm completely lost.
Any help would be appreciated.

 

[Pandasaurus]

I started to correct the math, then realized you were right (or I'm really bad at subnetting)... Which book is this?

 

[Janna1]

Which book is this?

CompTIA Network+® Certification Exam Guide, Sixth Edition
(Exam N10-006)
Mike Meyers

https://www.amazon.com/CompTIA-Network-Guide-Sixth-N10-006/dp/0071848223

 

[sdifox]

I don't get what the 2 to the power of 3 is about.

https://en.wikipedia.org/wiki/Subnetwork

that explains it rather well.

 

[drebo]

26 - 24 = 2, not 3. 2^2 = 4. A /24 contains four /26s.

What's the problem?

 

[Janna1]

26 - 24 = 2, not 3. 2^2 = 4. A /24 contains four /26s.

What's the problem?

The problem is the bizarre math explanation of 2^3=6 when going to /26. Not only is the 3 illogical since it should be 2, the equation doesn't even make sense.

After further reading, it only lists the 4 subnets created. And later on the book accurately shows that going to /27 creates 8 subnets, with the equation 2^3=8.

I'm going to put the nonsensical numbers given as a typo.
Problem solved. 🙂

 

[sdifox]

The problem is the bizarre math explanation of 2^3=6 when going to /26. Not only is the 3 illogical since it should be 2, the equation doesn't even make sense.

After further reading, it only lists the 4 subnets created. And later on the book accurately shows that going to /27 creates 8 subnets, with the equation 2^3=8.

I'm going to put the nonsensical numbers given as a typo.
Problem solved. 🙂

Email the author and ask.