Question

. Solve Problem 14.18 at the end of Chapter 14 (p.466). A copy of this problem is given here for your convenience: Given a company with six individual departments and each department having ten computers or networked devices, what mask could be applied to the company net- work to provide the subnetting necessary to divide up the network equally?

Answer 1

given 6 departments and 10 computers in each department.

no of bits required to represent 6 departments = 3 bits

no of bits required to represent 10 computers = 4 bits

since ip consists of network and host bits.  

so our network bits are (32-3-4)= 25 bits.

subnet bits= 3

host bits= 4

mask covers both network and subnet so the first 25+3 =28 bits are for mask

11111111.11111111.11111111.11110000 is the subnet mask (255.255.255.240) which allows 6 departments which allows 10 computers.

additional information:

with 4 bits total 2⁴-2 hosts are possible that is (16-2) = 14