IP addressing (classful): Which dotted format corresponds to a Class A network address layout?

Introduction / Context:
Before Classless Inter-Domain Routing (CIDR) became ubiquitous, IPv4 used classful addressing: Class A, B, and C networks had fixed boundaries for network and host portions. Recognizing these formats is useful for legacy exams and understanding historical configurations.

Given Data / Assumptions:

• IPv4 addresses are 32 bits, often written as four decimal octets.
• Class A: first octet is the network (8 bits), remaining three are hosts (24 bits).
• Question uses Net/Node placeholders to represent network vs host parts.

Concept / Approach:
In classful notation: Class A uses Net.Host.Host.Host, Class B uses Net.Net.Host.Host, Class C uses Net.Net.Net.Host. Therefore, for Class A, the correct pattern is Net.Node.Node.Node (one network octet followed by three host octets).

Step-by-Step Solution:

Verification / Alternative check:
Example: 10.0.0.1 is a classic Class A private block; 10 is the Net, and 0.0.1 are Nodes/hosts.

Why Other Options Are Wrong:
Net.Net.Node.Node: Class B. Net.Net.Net.Node: Class C. Net.Node.Net.Node: Not a valid classful split. None of the above: incorrect because Net.Node.Node.Node is correct.

Common Pitfalls:
Confusing classful with CIDR, where boundaries can be at any bit. Mixing up B and C masks in memory; use the mnemonic A=1 Net, B=2 Nets, C=3 Nets (in octets).

Final Answer:
Net.Node.Node.Node