# Examples

### **Problem-01:**

Given the CIDR representation 20.10.30.35 / 27. Find the range of IP Addresses in the CIDR block.

### **Solution-**

Given CIDR representation is 20.10.30.35 / 27.

It suggests-

* 27 bits are used for the identification of network.
* Remaining 5 bits are used for the identification of hosts in the network.

Given CIDR IP Address may be represented as-

00010100.00001010.00011110.00100011 / 27

So,

* First IP Address = 00010100.00001010.00011110.001**00000** = 20.10.30.32
* Last IP Address = 00010100.00001010.00011110.001**11111** = 20.10.30.63

Thus, Range of IP Addresses = \[ 20.10.30.32 , 20.10.30.63]

### **Problem-02:**

Given the CIDR representation 100.1.2.35 / 20. Find the range of IP Addresses in the CIDR block.

### **Solution-**

Given CIDR representation is 100.1.2.35 / 20.

It suggests-

* 20 bits are used for the identification of network.
* Remaining 12 bits are used for the identification of hosts in the network.

Given CIDR IP Address may be represented as-

01100100.00000001.00000010.00100011 / 20

So,

* First IP Address = 01100100.00000001.0000**0000.00000000** = 100.1.0.0
* Last IP Address = 01100100.00000001.0000**1111.11111111** = 100.1.15.255

Thus, Range of IP Addresses = \[ 100.1.0.0 , 100.1.15.255]

### **Problem-03:**

Consider a block of IP Addresses ranging from 100.1.2.32 to 100.1.2.47.

1. Is it a CIDR block?
2. If yes, give the CIDR representation.

### **Solution-**

For any given block to be a CIDR block, 3 rules must be satisfied-

### **Rule-01:**

* According to Rule-01, all the IP Addresses must be contiguous.
* Clearly, all the given IP Addresses are contiguous.
* So, Rule-01 is satisfied.

### **Rule-02:**

* According to Rule-02, size of the block must be presentable as 2n.
* Number of IP Addresses in the given block = 47 – 32 + 1 = 16.
* Size of the block = 16 which can be represented as 24.
* So, Rule-02 is satisfied.

### **Rule-03:**

* According to Rule-03, first IP Address must be divisible by size of the block.
* So, 100.1.2.32 must be divisible by 24.
* 100.1.2.32 = 100.1.2.0010**0000** is divisible by 24 since its 4 least significant bits are zero.
* So, Rule-03 is satisfied.

Since all the rules are satisfied, therefore given block is a CIDR block.