SUBNET Mask and IP address problem

Question

If the subnet mask is 255.255.255.224, which of the following addresses CANNOT be assigned to network hosts?

 A. 15.234.118.63

B. 92.11.178.93

C. 134.178.18.56  

D. 192.168.16.87 
 

Comments

A is directed broadcast address not a host address . A is answer.

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How it became a broadcast address? Please explain

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It is the first subnet  DBA.

Answer 1

NETMASK = 255.255.255.224

224 = 11100000

=> we have 5 host bits.

A) 63 = 00111111

B) 93 = 01011101

C) 56 = 00111000

D) 87 = 01010111

In A all 5 host bits are 1 => It is the directed broadcast address in 15.234.118.32 subnet.