Consider three machines M, N, and P with IP addresses 100.10.5.2, 100.10.5.5, and 100.10.5.6 respectively.

Q. Consider three machines M, N, and P with IP addresses 100.10.5.2, 100.10.5.5, and 100.10.5.6 respectively. The subnet mask is set to 255.255.255.252 for all the three machines. Which one of the following is true?

(A) M, N, and P all belong to the same subnet

(B) Only M and N belong to the same subnet

(C) Only N and P belong to the same subnet

(D) M, N, and P belong to three different subnets

Solution:

First, we will do bitwise AND between Subnet mask and given IP address one by one

For M: 100.10.5.2

Bitwise AND:

    01100100.00001010.00000101.00000010 (100.10.5.2)

AND 11111111.11111111.11111111.11111100 (255.255.255.252)

___________________________________________________________

   = 01100100.00001010.00000101.00000000 (100.10.5.0)

For N: 100.10.5.5

Bitwise AND:

    01100100.00001010.00000101.00000101 (100.10.5.5)

AND 11111111.11111111.11111111.11111100 (255.255.255.252)

___________________________________________________________

   = 01100100.00001010.00000101.00000100 (100.10.5.4)

For P: 100.10.5.2

Bitwise AND:

01100100.00001010.00000101.00000110 (100.10.5.6)

AND 11111111.11111111.11111111.11111100 (255.255.255.252)

___________________________________________________________

   = 01100100.00001010.00000101.00000100 (100.10.5.4)

It is sure from the above computation that N and P belong to the same network (i.e., 100.10.5.4), while M can belong to the same network or it can be from any other network.