You are given the network 192.168.1.0/24. To divide this network into two equal subnets, which of the following subnet masks would you use, and what are the resulting network ranges? (Select all that apply.)
Correct Answer: A,B
Detailed Explanation: Subnetting is a critical skill for network professionals, as it allows for efficient utilization of IP address space by dividing a larger network into smaller, manageable sub-networks. In this scenario, you are given a /24 network—specifically, 192.168.1.0/24—which provides 256 IP addresses (from 192.168.1.0 to 192.168.1.255). The task is to divide this network into two equal subnets. To split a /24 network into two equal parts, you need to use a subnet mask that provides half the number of available IP addresses per subnet compared to the original. A /24 network has 256 addresses; dividing this number by 2 gives you 128 addresses per subnet. The subnet mask that provides 128 addresses is /25, because a /25 network has 2^(32-25) = 2^7 = 128 addresses. When you apply a /25 subnet mask to the 192.168.1.0/24 network, it creates two subnets: Subnet 1: 192.168.1.0/25 Network address: 192.168.1.0 Broadcast address: 192.168.1.127 Usable IP range: 192.168.1.1–192.168.1.126 Subnet 2: 192.168.1.128/25 Network address: 192.168.1.128 Broadcast address: 192.168.1.255 Usable IP range: 192.168.1.129–192.168.1.254 Thus, option A correctly represents the first subnet, and option B correctly represents the second subnet. The choices that use a /26 mask (Options C and D) would divide the network into four equal subnets, not two, because a /26 provides 2^(32-26) = 64 IP addresses per subnet. Option E is incorrect because the /25 subnetting method is the proper approach to dividing a /24 network into two equal subnets. Understanding subnetting involves not only calculating the correct subnet mask but also determining the network and broadcast addresses for each subnet. The network address is always the first address in the subnet, while the broadcast address is the last. The range of usable IP addresses lies between these two addresses. For example, in the 192.168.1.0/25 subnet, the first address (192.168.1.0) is the network address, and the last address (192.168.1.127) is the broadcast address. The usable host addresses are therefore from 192.168.1.1 to 192.168.1.126. Proper subnetting is vital for designing efficient IP networks, reducing broadcast domains, and enhancing overall network performance. It also plays a significant role in security by logically separating network segments. In summary, to divide the 192.168.1.0/24 network into two equal subnets, you use a /25 subnet mask, which results in the subnets outlined in options A and B.
This CCNA practice question helps students prepare for Cisco networking certification exams by testing knowledge of network fundamentals, routing, switching, and network security concepts.