Subnetting and IP Addressing

Correct Answer: /16

The 10.0.0.0/8 network has a default mask of 8 bits which gives you one network with 16777214 usable hosts. The administrator wants to divide it into 200 subnets. Each subnet, therefore, would have a maximum of approximately 83886 hosts (16777214/200). To provide for this number of hosts, you would need a subnet mask of /16. Each /16 subnet provides 65534 usable host addresses (2^16 - 2), which is more than enough for our requirement. On contrary, a /17 subnet would provide only 32766 usable addresses which is not sufficient, while a /15 or a /14 subnet would provide more addresses per subnet than required leading to wastage of addresses. Therefore, the new subnet mask should be /16.

Correct Answer: /26

The subnet mask /26, or 255.255.255.192, is the minimum size that can support at least 62 hosts. This is because a /26 subnet mask provides up to 64 addresses, but 2 of these are reserved, the network address and the broadcast address, leaving 62 usable addresses. The other options are incorrect because /27 and /28 provide fewer addresses than required (30 and 14 usable addresses respectively), while /25 provides more addresses (126 usable) than needed, which can be inefficient.

Correct Answer: /28

The size of the subnet mask determines how many hosts can be supported on each network. The smallest subnet mask that can support at least 14 hosts is /28, which provides 16 IP addresses. However, 2 of these IP addresses are used for the network address and the broadcast address, which leaves 14 available for hosts. The choice of /27, /26, and /25 would provide more than 14 hosts which isn't necessary and it would be a waste of IP address space. Therefore, the smallest possible subnet mask that can support at least 14 hosts for each VLAN is /28.