Question

Which one of the following CIDR prefixes exactly represents the range of IP addresses $10.12.2.0$ to $10.12.3.255$?

• A. $10.12.2.0/23$
• B. $10.12.2.0/24$
• C. $10.12.0.0/22$
• D. $10.12.2.0/22$

Hint:

To find the correct CIDR prefix, calculate the subnet mask and verify the range of IPs it covers.

Answer 1

The Correct Option is A

The given range is $10.12.2.0$ to $10.12.3.255$.
The CIDR notation $10.12.2.0/23$ has a subnet mask of $255.255.254.0$, which covers the following range of IPs: $$10.12.2.0 \, \text{(start)} \, \text{to} \, 10.12.3.255 \, \text{(end)}.$$ Other options do not correctly represent this range:
(B) $10.12.2.0/24$: Only covers $10.12.2.0$ to $10.12.2.255$.
(C) $10.12.0.0/22$: Covers a larger range from $10.12.0.0$ to $10.12.3.255$.
(D) $10.12.2.0/22$: Invalid as it overlaps incorrectly with the range $10.12.4.x$. Final Answer: $$\boxed{\text{(A)}}$$