220-801 · Question #193
Which of the following is the subnet mask for a Class A IP address?
The correct answer is B. 255.0.0.0. IP address classes have fixed default subnet masks. Class A addresses (first octet 1–126) use 255.0.0.0, meaning only the first 8 bits identify the network and the remaining 24 bits identify hosts - allowing over 16 million hosts per network. Class B uses 255.255.0.0 and Class…
Question
Which of the following is the subnet mask for a Class A IP address?
Options
- A127.0.0.1
- B255.0.0.0
- C255.255.255.0
- D255.255.255.254
How the community answered
(66 responses)- A5% (3)
- B92% (61)
- C2% (1)
- D2% (1)
Explanation
IP address classes have fixed default subnet masks. Class A addresses (first octet 1–126) use 255.0.0.0, meaning only the first 8 bits identify the network and the remaining 24 bits identify hosts - allowing over 16 million hosts per network. Class B uses 255.255.0.0 and Class C uses 255.255.255.0. Option A (127.0.0.1) is the loopback address, not a subnet mask. Option D (255.255.255.254) is not a standard classful subnet mask.
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