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I could use some help with my way of calculating usable subnets and usable hosts.

the way i normally do it:
169.199.109.137 (class B)
255.255.255.192

network | host
169.199 | 109.137
255.255 | 255.192 = 11111111.11000000 = 10(1) 6(0)

2^10 = 1024 usable subnets
2^6 = 64-2 = 62 usable hosts

that is the way I normally do it but my teacher would like to me use another method since i have use my own method wrong on multiple occasions.

His version:
222.152.18.64 (class C)
255.255.255.248

network bits (n), subnet bits (s) and host bits (h)
nnnnnnnn.nnnnnnnn.nnnnnnnn.sssshhhh
then from that he gets the numbers he needs above the 2^?

2^? = ? usable subnets
2^? = ?-2 = ? usable hosts

I don't understand how his way works, how he gets the correct amount of n, s and h, and what to place above the 2^

I am one week into learning about ip's and subnetting, so when you give me a way to learn his way do explain it so I would understand it.

JelmerS
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Skovdam
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1 Answers1

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Your teachers way and your way are exactly the same, just written down differently. To use your way as the teachers way, replace the 1's you wrote down with s and the 0's with h. So:

network | host
169.199 | 109.137
255.255 | 255.192 = 11111111.11000000 =       10(1) 6(0)
nnnnnnnn.nnnnnnnn | ssssssss.sshhhhhh = 16(n) 10(s) 6(h)

2^s = 1024 usable subnets 2^h = 64-2 = 62 usable hosts

JelmerS
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