
Explanation:
An IPv4 address consists of 32 bits. The first x number of bits in the address is the network address and the remaining bits are used for the host addresses. The subnet mask defines howmany bits form the network address and from that, we can calculate how many bits are used for the host addresses.
The formula to calculate the number of hosts in a subnet is 2n - 2. The "n" in the host's formula represents the number of bits used for host addressing.If we apply the formula (22 - 2), we can determine that the following subnets should be configured:
Sales network - /26 - This will provide up to 62 usable IP addresses (64-2 for subnet and broadcast IP) HR network - /27 - This will provide for up to 30usable IP's (32-2) IT - /28 - This will provide for up to 14 usable IP's (16-2) Finance - /26 - Note that a /27 is 32 IP addresses but 2 of those are reserved for the network and broadcast IP's and can't be used for hosts.
Marketing - /28
If we add up howmany IP blocks are used that is 64+32+16+64+16=192.
A /24 contains 256 IP addresses, so 256-192=64.
So the last unused box should be a /26, which equates to 64 addresses