GATE CSE 2024 | Set 2 | Question: 28

Question

​​​​​Which one of the following $\text{CIDR}$ prefixes exactly represents the range of $\text{IP}$ 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. $10.12 .2 .0 / 22$

Answer 1

Correct Answer is A.

Consider the IP address = 10.12.2.0 and its binary equivalent is given as 

0000 1010. 0000 1100. 0000 0010. 0000 0000. Thus if the end IP needs to be 10.12.3.255 then the CIDR notation needs to be 10.12.2.0/23. Hence Option (A) seems to be correct.

Answer 2

As, the Ip addresses are contiguous,Block size is power of 2,and starting address is divisible by block size so, they can form a block 

 

Answer 3

Ans (A) : 10.12.2.0/23

10.12.2.0 : 10.12.00000010.00000000   and to end with 10.12.3.255 (10.12.00000011.11111111 )

the common bits between the start and the end address are 0000001 
prefix will be 32-9 = 23

10.12.2.0/23 is correct
 

Answer 4

Well We Know That CIDR Representatiion comes under Classless Addressing and in it , all the IP addresses are contiguous .

Hence The range from 10.12.2.0 to 10.12.3.255 involves , 2^9 IP addresses in total { 10.12.2.0 -> 10.12.2.255  , 10.12.3.0 -> 10.12.3.255 }

Hence , HID contains 9bits , so NID = 32 - HID = 23bits 

Hence The CIDR representation would be : 10.12.2.0/23