# 10.7.1 Skills Integration Challenge – Network Planning and Interface Configuration

31 Mar 2013
kenglong@gmail.com

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Binary reference charts

### The Requirements

This exercise requires us to create an efficient addressing plan using variable length subnetting given the following:

• `192.168.1.0 /24`
• One subnet with 60 hosts
• One subnet with 25 hosts
• One subnet with 10 hosts
• One subnet with 7 hosts
• Three subnets with 2 hosts each for router interconnections.

### Step-by Step

The steps to solve this are as follows:

1. Start with the network with the most hosts
1. Find the subnet mask
1. Find the first power of two that is equal to or greater than the number of hosts. That is the number of host bits in our subnet mask.
2. Subtract that power of two from 32, the total number of bits in the subnet mask. This gives us the number of network bits or cidr.
3. Find the "magic" number. (The magic number is the place holder of the first high bit from the right in the octet of interest. In our case here, it's the fourth octet.)
4. Convert the binary mask you just created from the host bits (zeros) and network bits (ones) to decimal.
2. Find the next network number
1. Add the magic number to the beginning network number to get the next network number. This is our framework for finding the first host, last host and broadcast. The next network number is also the beginning network for the next part of the problem.
2. Use the second network number as the starting point for the next part of the problem and repeat the above steps.

### The Solution

Now, try to solve the subnetting exercise on your own. If you get stuck, see the solution here.