172.17.20.0
255.255.0.0
1111 1111.1111 1111.0000 0000.0000 0000
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172.17.20.0 /16
Let's say we have this IP
And we have this subnet Mask
If we look at the Subnet Mask in Binary and count the bits we get ..
The shorthand allows us to use the bit number to represent the mask