Which of the following IPv4 address ranges are reserved for private networks? (Select all that apply.)
Correct Answer: A,B,C
Detailed Explanation: IPv4 private address ranges are reserved for use within private networks and are not routable on the public Internet. These address ranges were established by RFC 1918 to help alleviate the shortage of public IPv4 addresses and to allow organizations to use IP addressing schemes internally without conflicting with globally routable addresses. A. 10.0.0.0 to 10.255.255.255: This range provides a large block of addresses and is often used in very large networks or organizations that require many subnets. The entire 10.x.x.x space is reserved for private use, making Option A correct. B. 172.16.0.0 to 172.31.255.255: This range covers 16 contiguous Class B networks. It offers a moderate amount of address space and is frequently used by organizations that do not require the vast number of addresses provided by the 10.x.x.x range. Option B is correct. C. 192.168.0.0 to 192.168.255.255: This range is the most commonly used for small to medium-sized networks, such as home networks and small businesses. The 192.168.x.x space is easy to remember and widely implemented in consumer-grade networking equipment, making Option C correct. D. 192.0.2.0 to 192.0.2.255 (Incorrect): This range is designated as a TEST-NET, reserved for documentation and example purposes in technical documents (as defined by RFC 5737). It is not available for private addressing within operational networks. Importance in Network Design: Understanding private IP address ranges is crucial for network design and security. Private addresses are used in conjunction with Network Address Translation (NAT) to allow internal networks to communicate with the public Internet while conserving public IP addresses. By using reserved private address ranges, organizations can structure their networks in a way that is independent of public address constraints, while still maintaining the ability to reach external networks through NAT or VPNs. Application in Troubleshooting: When troubleshooting IP addressing issues, knowing the difference between private and public address spaces is essential. It helps network administrators determine whether a device is using a valid address for internal communication and whether NAT is functioning correctly for Internet-bound traffic. Conclusion: The IPv4 private address ranges are 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 (Options A, B, and C). The range 192.0.2.0/24 is reserved for documentation and testing purposes and is not intended for private network use (making Option D incorrect). Mastery of these ranges is a foundational aspect of IP addressing and network design.
This CCNA practice question helps students prepare for Cisco networking certification exams by testing knowledge of network fundamentals, routing, switching, and network security concepts.