GATE CS 2024 Set 2 Q.38: IPv4/IPv6 Addressing, Subnetting, CIDR, ARP, ICMP and NAT

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

10.12.2.0/23

10.12.2.0/24

10.12.0.0/22

10.12.2.0/22

Official answer and solution

Official answer: A
From: Official GATE 2024 answer key

Solution

Compare the binary representations of the third and fourth octets of 10.12.2.0 and 10.12.3.255.

Writing the last two octets in binary:

10.12.2.0 $= \texttt{10.12.00000010.00000000}$
10.12.3.255 $= \texttt{10.12.00000011.11111111}$

The first $8 + 8 + 7 = 23$ bits (10.12.0000001_) are identical across the entire range, while the remaining $32 - 23 = 9$ bits vary through all $2^9 = 512$ combinations from all 0s to all 1s. Thus the exact CIDR prefix is 10.12.2.0/23.

Final answer

Option (A)

The answer is the one in the official GATE answer key. The solution is this site's own explanation.

Source

Paper: GATE 2024 Computer Science and Information Technology - Set 2 (CS2)
Question: 38 of 65
Section: Computer Science and Information Technology

Report an error in this question

GATE questions are the work of the organising institutes. This site is independent and is not affiliated with them.

Question

Solution

Source