What are the CIDR addresses for a network if all its address

What are the CIDR addresses for a network if all its addresses start with 145.98? And if this network has exactly two subnets, what are the CIDR addresses for each of its subnets?

Solution

145.98 = 10010001.01100010

Then there are 2^32-16 = 2¹⁶ addresses possible. The range of addresses is from 145.98.0.1 to 145.98.255.255

If there are 2 subnets, 1 bit will be used for the subnet. So each subnet will have 2^32-17 = 2¹⁵ addresses.

For subnet 1 range of IP shall be 145.98.0.1 to 145.98.127.255

For subnet 2, the range of IP shall be 145.98.128.1 to 145.98.255.255