Private IP Address host range

Hi,
I know the Private Address range is
10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.31.255.255
192.168.0.0 - 192.168.255.255
with default subnet masks as per classes
but when i am trying to find how many hosts in private ip address range i found in wikipedia
172.16.0.0 -172.31.255.255 /12
i don't understand why 12bits are network bits

Comments

  • JoeMJoeM ✭✭✭

    Great practice question. Notice where the mask bits line up with the possible networks. Anything to the right of the network addresses would be potential hosts.

    172.16.0.0 - 172.31.255.255

         172      16
     10101100    0001 0000 
    
         172      31
     10101100    0001 1111
    
            /12
     11111111    1111
    

    It is important to understand that the subnet mask can be anything /12+ -- as long as it is between 12 and 32. Anything shorter would fall outside the private range. This would also change your number of possible hosts.

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