Could someone clarify what these notations for subnets mean?
The /24 means we look at the first 24 bits of the address while the /21 means we look at the first 21 bits to match them to the subnets. I think.
To expand a bit more, i think the '/k' notation refers to the first 'k' bits of the address that we want to match. You would want to convert the first 'k' bits of the subnet mask and the address to binary and perform an AND operation.