Question 1
Link to questionA network administrator is tasked with designing a subnetting scheme for a company that has been allocated the IP address range of 192.168.1.0/24. The company requires at least 6 subnets to accommodate different departments, and each subnet must support at least 30 hosts. What subnet mask should the administrator use to meet these requirements, and how many usable IP addresses will each subnet provide?
255.255.255.224 (Subnet mask: /27, 30 usable IPs)
255.255.255.192 (Subnet mask: /26, 62 usable IPs)
255.255.255.240 (Subnet mask: /28, 14 usable IPs)
255.255.255.248 (Subnet mask: /29, 6 usable IPs)
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Correct answer
255.255.255.224 (Subnet mask: /27, 30 usable IPs)
Next, we need to ensure that each subnet can support at least 30 hosts. The formula for calculating the number of usable hosts in a subnet is \2^h - 2\, where \h\ is the number of host bits. The \"-2\" accounts for the network and broadcast addresses. To find the number of host bits needed, we set up the inequality \2^h - 2 \\geq 30\. The smallest \h\ that satisfies this is 5, since \2^5 - 2 = 30\. Now, we can calculate the subnet mask. The original subnet mask for a /24 network has 24 bits for the network and 8 bits for hosts. If we use 3 bits for subnetting, we have \24 + 3 = 27\ bits for the subnet mask. This means we will have a subnet mask of /27, which corresponds to 255.255.255.224. With a /27 subnet mask, we have 5 bits left for hosts, allowing for \2^5 - 2 = 30\ usable IP addresses per subnet. This meets both the requirement for the number of subnets and the number of hosts per subnet. Thus, the correct subnet mask is 255.255.255.224, providing 30 usable IP addresses for each of the 8 subnets created.
