Question

Your ISP has given you the following CIDR address 196.92.21.0/24. This address will be split among 3 facilities each with its own subnet consisting of 64 addresses each. Out of the remaining 64 addresses 32 will be split into two subnets for the administrative and accounting departments with 16 addresses each. The remaining addresses will be allocated for guests' access. Write the address range for each subnet in CIDR notation. Show all your workings.

Answer 1

So as we have in total of 256 addresses for the host.
So we need 8 bits from the host side and thus we will use 2 bits to divide it into 4 subnets and then we will use remaining of 6 bits out of 8 for host addresses.

So first dividing the network into 4 subnets as follows:

196.92.21.0 - 63 / 26 :: Facility 1
196.92.21.64 - 127 / 26 :: Facility 2
196.92.21.128 - 191 / 26 :: Facility 3
196.92.21.192 - 255 / 26

So from above 4, we can directly allocate the first 3 to the 3 facilities and we can divide the later one into further subnets.

So now there are two subnets which require 16 hosts, so which can be provided using 4 bits. So the remaining 28 bits would be there for the host.

196.92.21.192 - 207 / 28 :: Administrative
192.92.21.208 - 223 / 28 :: Accounting

So the remaining one facility requires 32 hosts. So require 5 bits so it would be 27 for network and 5 for the host.

192.92.21.224 - 255 / 27 :: Guests

So above is the overall way in which the network would be divided.

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