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1 votes
1 votes
Suppose computer A and B have IP address
143.105.1.113 and 143.105.1.91 respectively
and they use the same subnet mask N. Which
of the values of N given below should NOT
be used if A & B belongs to the same
network—
(A) 255.255.255.0
(B) 255.255.255.128
(C) 255.255.255.192
(D) 255.255.255.224

1 Answer

Best answer
2 votes
2 votes

Here we have to find the subnet mask for which both IP addresses belongs to the different network. ie. When we do Bitwise AND of IP addresses and that subnet mask, result should be different network id.

Option a) 143.105.1.113 & 255.255.255.0 = 143.105.1.0 , 143.105.1.91 & 255.255.255.0= 143.105.1.0

Option b) 143.105.1.113 & 255.255.255.128 = 143.105.1.0 , 143.105.1.91 & 255.255.255.128= 143.105.1.0

Option c) 143.105.1.113 & 255.255.255.192 = 143.105.1.64 , 143.105.1.91 & 255.255.255.192= 143.105.1.64

Option d)  143.105.1.113 & 255.255.255.224 = 143.105.1.96 , 143.105.1.91 & 255.255.255.224= 143.105.1.64

So subnet mask 255.255.255.224 should not be chosen, otherwise A and B will be in different network.

Hence Option d) is correct

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