How you work out the number of valid host IP addresses per subnet?

Host address 192.20.2.130

Subnet mask 255.255.255.224

your subnet : 255.255.255.224 is binary

11111111.11111111.11111111.11100000

so you have 5 host bits available to distribute for IP adresses. Then you do 2^5(squared) because a bit can be 1 or 0, so you get 30 IP's on this subnet. (actually 32, but you can't use all 0's and all 1's)

Because you have 3 subnet bits, you have 2^3 (squared) subnets so 8 subnets

Subnets :

192.20.2.0

192.20.2.32

192.20.2.64

192.20.2.96

192.20.2.128 -> the range you are in, but because you can't have all 1's and all 0's, this is 130 for the ip adress

192.20.2.160

192.20.2.192

192.20.2.224

(note that the last number is the same as the subnet masks last number)

Host Id ranges :

192.20.2.1 - 192.20.2.30

192.20.2.33 - 192.20.2.62

192.20.2.65 - 192.20.2.94

192.20.2.97 - 192.20.2.126

192.20.2.130 - 192.20.2.158

192.20.2.160 - 192.20.2.190

192.20.2.192 - 192.20.2.224

With thanks to the next user for pointing out m mistake ;-)

To previous answerer: very well explained. I love doing bits & bytes!!

There was just one mistake - it's 2^5 , not 5^2.

So the real number of valid hosts would be:

2^5 - 2 = 30

30

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