As we have already learned about Classful Addressing, so in this article, we are going to learn about Classless Inter-Domain Routing. which is also known as Classless addressing. In the Classful addressing the no of Hosts within a network always remains the same depending upon the class of the Network.
Class A network contains 224 Hosts, Class B network contains 216 Hosts, Class C network contains 28 Hosts
Now, let’s suppose an Organization requires 214 hosts, then it must have to purchase a Class B network. In this case, 49152 Hosts will be wasted. This is the major drawback of Classful Addressing.
In order to reduce the wastage of IP addresses a new concept of Classless Inter-Domain Routing is introduced. Now a days IANA is using this technique to provide the IP addresses. Whenever any user asks for IP addresses, IANA is going to assign that many IP addresses to the User.
Representation: It is as also a 32-bit address, which includes a special number which represents the number of bits that are present in the Block Id.
a . b . c . d / n
Where, n is number of bits that are present in Block Id / Network Id.
Rules for forming CIDR Blocks:
- All IP addresses must be contiguous.
- Block size must be the power of 2 (2n).
If the size of the block is the power of 2, then it will be easy to divide the Network. Finding out the Block Id is very easy if the block size is of the power of 2.
If the Block size is 25 then, Host Id will contain 5 bits and Network will contain 32 – 5 = 27 bits.
- First IP address of the Block must be evenly divisible by the size of the block. in simple words, the least significant part should always start with zeroes in Host Id. Since all the least significant bits of Host Id is zero, then we can use it as Block Id part.
Check whether 18.104.22.168 to 22.214.171.124 is a valid IP address block or not?
- All the IP addresses are contiguous.
- Total number of IP addresses in the Block = 16 = 24.
- 1st IP address: 100.1.2.00100000
Since, Host Id will contains last 4 bits and all the least significant 4 bits are zero. Hence, first IP address is evenly divisible by the size of the block.
All the three rules are followed by this Block. Hence, it is a valid IP address block.
Attention reader! Don’t stop learning now. Get hold of all the important CS Theory concepts for SDE interviews with the CS Theory Course at a student-friendly price and become industry ready.
- Difference between Classful Routing and Classless Routing
- Inter VLAN Routing by Layer 3 Switch
- Collision Domain and Broadcast Domain in Computer Network
- Difference between Distance vector routing and Link State routing
- Unicast Routing - Link State Routing
- CIDR Full Form
- IP Addressing | Classless Addressing
- IPv4 Classless Subnet equation
- Classful Vs Classless Addressing
- Inter Process Communication (IPC)
- Inter-Switch Link (ISL) and IEEE 802.1Q
- Difference between Inter and Intra Frame Compression
- What is ISL(Inter-Switch Link)?
- Domain Name System (DNS) in Application Layer
- Address Resolution in DNS (Domain Name Server)
- Introduction of Active Directory Domain Services
- Domain Key Normal Form in DBMS
- Creating custom domain name instead of localhost in Ubuntu
- Domain Relational Calculus in DBMS
- Difference between Tuple Relational Calculus (TRC) and Domain Relational Calculus (DRC)
If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to firstname.lastname@example.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.