networking - How to find Subnets and Hosts from given IP -

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i have been learning subnetting exam , came through question. enter image description here

but why this? first thought: 172.20.0.0 can have 254 subnets , 254 hosts per each subnet. wrong. can please explain me how this?

thanks guys

the netmask 255.255.252.0 has 10 0 bits @ end.
2 ^ 10 = 1024, minus broadcast , network address = 1022.

if you're using classful way of dividing network, 172.20.* b network, 16 bit size of network part. gives 16-10 = 6 bits spare, can split 2 ^ 6 = 64 networks.


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