The IP Address 10.10.10.1 belongs to which class?

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

Answer: (A)

In classful addressing, the class is determined by the value of the first octet. Class A uses first octet values from 0 to 127, with a default subnet mask of 255.0.0.0. The address 10.10.10.1 starts with 10, which falls in 0–127, so it is a Class A address. Note that 10.0.0.0/8 is a private address range, but that doesn’t change its class. Class B would start with 128–191, Class C with 192–223, and Class D with 224–239.