Cisco Certified Network Associate (CCNA) Practice Exam

With a subnet mask of 255.255.255.224, which of the following addresses can be assigned to network hosts?

1. 15.234.118.63

2. 92.11.178.93

3. 134.178.18.56

4. 192.168.16.87

The correct answer is: 92.11.178.93

To determine which of the given addresses can be assigned to network hosts within a subnet defined by the mask 255.255.255.224, it's necessary to understand the implications of this subnet mask. A subnet mask of 255.255.255.224 indicates that the first 27 bits (8+8+8+3) are used for the network portion, leaving 5 bits available for host addresses. With 5 bits for host addresses, the number of possible addresses in a subnet is calculated as 2^5 = 32. However, two addresses are reserved: one for the network address (the first address in the subnet) and one for the broadcast address (the last address in the subnet). Therefore, the usable addresses for hosts in each subnet become 32 - 2 = 30. To identify valid host addresses among the provided options, we need to determine which of the addresses fall into a subnet that permits host assignments. The subnet mask also helps in establishing what the network address is for each provided IP address. In the case of the answer identified as valid (92.11.178.93), we can analyze it: - The binary representation of the last octet (178) is `10110010