GATE CS 2024 Set 2 — Question 38

MCQ+2 / -0.67EasySubnetting & CIDRNetwork Layer: AddressingComputer Networks

Computer Networks → Network Layer: Addressing → Subnetting & CIDR

Last updated 20 August 2026

Question

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

Correct answer (A) 10.12.2.0/23 Solution The range of IP addresses is from 10.12.2.0 to 10.12.3.255. Let's look at the binary representation of the third octet, as the first two octets (10.12) are constant. 2 in binary: 00000010 3 in binary: 00000011 The range covers exactly these two values in the third octet, and for each value, the fourth octet ranges from 0 to 255. This corresponds to combining two consecutive /24 blocks: 10.12.2.0/24 and 10.12.3.0/24 . Comparing the binary of the third octet: 0000001000000011 The first 7 bits are identical (0000001). Total prefix length = 8 (1st octet) + 8 (2nd octet) + 7 (3rd octet) = 23 bits. The network address is the lowest address in the block: 10.12.2.0. Thus, the CIDR prefix is 10.12.2.0/23 . Turn this into a strength. Explore AI-powered practice and doubt support with Success Tracker.

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Correct answer (A) 10.12.2.0/23 Solution The range of IP addresses is from 10.12.2.0 to 10.12.3.255. Let's look at the binary representation of the third octet, as the first two octets (10.12) are constant. 2 in binary: 00000010 3 in binary: 00000011 The range covers exactly these two values in the third octet, and for each value, the fourth octet ranges from 0 to 255. This corresponds to combining two consecutive /24 blocks: 10.12.2.0/24 and 10.12.3.0/24 . Comparing the binary of the third octet: 0000001000000011 The first 7 bits are identical (0000001). Total prefix length = 8 (1st octet) + 8 (2nd octet) + 7 (3rd octet) = 23 bits. The network address is the lowest address in the block: 10.12.2.0. Thus, the CIDR prefix is 10.12.2.0/23 .

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