Assuming that your company uses the class a network 100.0.0.0/8, with what subnet mask would you need to configure all computers on the network to divide this network 11 times to match the comany's 11 departments?

Class A network 100.0.0.0/8, we need to divide it so that it can use 11 department, therefore 2^{4} = 16 maximum subnet. The subnet mask 255.240.0.0/12. The hosts per subnet are 2^20 = 1048574. The first 5 subnet range is attached with this question.

Explanation:

The IP address is 32 bits, The default subnet of class A is 255.0.0.0/8, but in this case we take 4 bits from host and add it to network bits so 8+4 = 12, that's why mask bit is 12.

8 bits   + 8 bits  +  8 bits  + 8 bits

100       .    0       .     0       .      0

we take 4 bits from 2nd octet so that it can use in 11 departments, so the remaining  4 bits + 8 bits + 8 bits = 20 bits

2^{20} = 1048574 hosts in each subnet

2^ {4} = 16 subnet ( 0 to 15 range)

when we subtract 255-15 = 240 so that the subnet mask is 255.240.0.0 / 12

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