Which of the following IPv4 address ranges is the Class A private address space defined by RFC 1918?

Introduction / Context:
Private IPv4 address ranges are reserved for use inside organizations and are not routable on the public Internet. They are defined in RFC 1918 and are commonly used in home, enterprise, and data center networks. Recognizing which ranges belong to which historical classes helps in configuring routers, firewalls, and NAT policies.

Given Data / Assumptions:

• We focus on the Class A private range as defined by RFC 1918.
• Several candidate address ranges are listed, some of which are other private ranges or special-purpose blocks.
• Only one option represents the correct Class A private address space.
• We assume standard IPv4 and traditional classful terminology.

Concept / Approach:
RFC 1918 specifies three private address ranges: 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. Historically, 10.0.0.0/8 is associated with Class A, 172.16.0.0/12 with Class B, and 192.168.0.0/16 with Class C. The 10.0.0.0/8 range covers 10.0.0.0 through 10.255.255.255, making it the correct Class A private range.

Step-by-Step Solution:
1. Recall that RFC 1918 defines 10.0.0.0/8 as a private block.2. The /8 mask means that the first octet, 10, is the network portion and the remaining three octets can vary.3. This yields a range from 10.0.0.0 up to 10.255.255.255.4. Compare this with the options and identify the range that exactly matches 10.0.0.0 – 10.255.255.255.5. Therefore, option A is the correct Class A private address space.

Verification / Alternative check:
Consulting documentation or networking references on RFC 1918 confirms that 10.0.0.0/8 is reserved for private use and is often used in large enterprise environments due to its large number of available addresses.

Why Other Options Are Wrong:
Option B, 172.16.0.0 – 172.31.255.255, is the Class B style private range defined by RFC 1918. Option C, 192.168.0.0 – 192.168.255.255, is associated with the Class C style private range. Option D, 169.254.0.0 – 169.254.255.255, is the link-local range used for automatic private IP addressing when DHCP fails and is not part of the RFC 1918 private ranges.

Common Pitfalls:
Learners sometimes mix up the different private ranges or think that any non-routable address is part of RFC 1918. It is important to memorize the three blocks and associate them with their typical usage sizes: very large 10.0.0.0/8, medium 172.16.0.0/12, and smaller 192.168.0.0/16.

Final Answer:
10.0.0.0 – 10.255.255.255