Tuesday, September 30, 2008

Classful Vs Classless Address

Hello friends in this post i am again going to tell you some more interesting concepts of networking.In this post i am going to tell you what is the difference between classfull and classless address.
Classful addressing:In the classful addressing system all the IP addresses that are available are divided into the five classes A,B,C,D and E, in which class A,B and C address are frequently used because class D is for Multicast and is rarely used and class E is reserved and is not currently used.Each of the IP address belongs to a particular class that's why they are classful addresses.Earlier this addressing system did not have any name,but when classless addressing system came into existence then it is named as Classful addressing system.The main disadvantage of classful addressing is that it limited the flexibility and number of addresses that can be assigned to any device.One of the major disadvantage of classful addressing is that it does not send subnet information but it will send the complete network address. The router will supply its own subnet mask based on its locally configured subnets. As long as you have the same subnet mask and the network is contiguous, you can use subnets of a classful network address.

For more details , please visit here and here.

Classless Addressing:Classless addressing system is also known as CIDR(Classless Inter-Domain Routing).Classless addressing is a way to allocate and specify the Internet addresses used in inter-domain routing more flexibly than with the original system of Internet Protocol (IP) address classes.What happened in classful addressing is that if any company needs more than 254 host machines but far fewer than the 65,533 host addresses then the only option for the company is to take the class B address.Now suppose company needs only 1000 IP addresses for its host computers then in this (65533-1000=64533) IP addresses get wasted.For this reason, the Internet was, until the arrival of CIDR, running out of address space much more quickly than necessary. CIDR effectively solved the problem by providing a new and more flexible way to specify network addresses in routers.A CIDR network address looks like this:

For more details , please visit here and here.

The "" is the network address itself and the "15" says that the first 15 bits are the network part of the address, leaving the last 17 bits for specific host addresses.One more advantage of classless addressing is that classless protocol sends subnet information. This allows you to create discontiguous networks with any given classful network address.

 For more details , please visit here and here.


anuj said...

It is an article which tells you the basic concept of networking and it's advantages.

Rajesh verma

Manno said...

this article is good but it classless addressing some concept is mising that how 1st 15bits reserve for nerwork while the address given in the exmple is of class B which already has 1st 16 bits for network.

kwidproknot said...

the example shown is in a class C.

anaklelakilaut said...

i think think the "byte" is wrong in the picture. it should be bit

d '}{' b said...

This guy is right, it should be bits, not bytes.. you have 32 bits in an ipv4 address.. which is a total of 4 bytes.. and not 32 bytes.. anyway.. just browsing here, it's for your own sake and also not misleading other browsers.. =) Good work

hitu said...

This is one of the best portal where all can share the knowledge of networking..
looking forward more concepts !!

mohammed said...

I am very thankful for your cooperation>>>

Bhavin said...

Jay Swaminarayan
Jay Bhagavan
Jay Mataji
Thank u

vishal Ithape said...

Aah that should be bits not bytes damn.IP V4 is of 4 bytes.

Saurav said...

@All yea guys agreed it should me bits not bytes...its my bad ... will upload image wd the correction.

Thanks for pointing it out.