In which octet of an IP address can you identify the class of the address?

In which octet of an IP address can you identify the class of the address?

• A. First
• B. Second
• C. Third
• D. Fourth

Answer: (A)

In the old classful IPv4 addressing system, the class of an address is determined by the value in the first octet. The first octet sets the class: 1–126 for Class A (with 127 reserved for loopback), 128–191 for Class B, 192–223 for Class C, 224–239 for Class D, and 240–255 for Class E. Because these class boundaries are defined by that initial octet, you can identify the class just by looking at the first octet; the remaining octets define the host portion or are used for subnetting, but they don’t determine the class itself. So, the correct idea is that the class is identified by the first octet. For example, a first octet of 10 indicates Class A, 172 indicates Class B, and 192 indicates Class C.

In the old classful IPv4 addressing system, the class of an address is determined by the value in the first octet. The first octet sets the class: 1–126 for Class A (with 127 reserved for loopback), 128–191 for Class B, 192–223 for Class C, 224–239 for Class D, and 240–255 for Class E. Because these class boundaries are defined by that initial octet, you can identify the class just by looking at the first octet; the remaining octets define the host portion or are used for subnetting, but they don’t determine the class itself.

So, the correct idea is that the class is identified by the first octet. For example, a first octet of 10 indicates Class A, 172 indicates Class B, and 192 indicates Class C.