What range of first octet values defines Class A IPv4 addresses?

Class A IPv4 addresses are defined by their first octet values, which range from 1 to 126. This classification scheme was established as part of the Internet Protocol, where different classes of addresses are used to allocate IP addresses based on network size.

Class A addresses are designed for very large networks. The first octet in a Class A address represents a significant portion of the address space, allowing for a vast number of hosts within a single network. The range starts at 1, which is often reserved for network identification, and goes up to 126, with 127 typically reserved for loopback addresses. This provides a substantial number of available addresses, which is suitable for large organizations or ISPs that need to connect many devices.

The ranges that define Classes B, C, and D do not apply here as they fall outside the boundaries for Class A. Class B uses the range 128 to 191, Class C goes from 192 to 223, while Class D, used for multicast groups, spans from 224 to 239. Therefore, the correct identification of Class A addresses by their octet range is crucial for understanding IP address allocation and classification in networking.