An IP address that begins with 10.x.x.x is part of which class?

• A. Class A
• B. Class B
• C. Class C
• D. Class D

Answer: (A)

Classful IP addressing uses the first octet to determine the class. Class A covers first octet values from 1 through 126, with the network portion being the entire first octet. An address that begins with 10 falls inside that 1–126 range, so it is categorized as Class A. Note that the 10.0.0.0/8 block is also designated for private networks, which affects routability on the public Internet but not the class determination itself.