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When we already have classFull Addressing Scheme in which we divided the IP addresses into Class A , Classs B , Class C , Class D and Class E then what was limitation in this that we need to introduce ClassLess IP addressing?

Can anyone tell please what happens in ClassLess IP addressing scheme and what was drawback that classless came from classfull.
asked in Computer Networks by Active (5k points) | 235 views

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Classful addressing divides an IP address into the Network and Host portions along octet boundaries. Classless addressing treats the IP address as a 32 bit stream of ones and zeroes, where the boundary between network and host portions can fall anywhere between bit 0 and bit 31. The network portion of an IP address is determined by how many 1's are in the subnet mask. Again, this can be a variable number of bits, and although it can fall on an octet boundary, it does not necessarilly need to. A subnet mask is used locally on each host connected to a network, and masks are never carried in IPv4 datagrams. All hosts on the same network are configured with the same mask, and share the same pattern of network bits. The host portion of each host's IP address will be unique. "

Classful addressing assigns an organization a Class A, Class B, or Class C block of addresses. Classless addressing assigns an organization a block of contiguous addresses based on its needs."

All IP addresses have a network and host portion. In classful addressing, the network portion ends on one of the separating dots in the address (on an octet boundary). Classless addressing uses a variable number of bits for the network and host portions of the address. "
answered by Active (3.3k points)
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dear sir i know classfull Ip addressing.

I was asking about ClassLess IP Adressing . in your entire explanation you told about classfull.

I want to know about classless please please please

Please read it carefully In first paragraph only first line describes classful addressing remaining is all about classless addressing if u want example

Classless IP addressing means you can use any subnetmask you want, even assigning partial blocks. For example subnet is a class B network.

But you have two physical interfaces on your router that connect to switches with 5 VLANs. Classless routing allows me to break up this IP address into more useful segments.

Switch 1                                   Switch 2

VLAN1               VLAN10

VLAN2               VLAN11

VLAN3               VLAN12

VLAN4               VLAN13

VLAN5               VLAN14

So I have made 10 useful subnets from a single network. Here's the real advantage:

1. When my router is configured for classless routing it can advertise all 10 networks as one IP address, or I can advertise each physical interface using and using ths subnet mask

In short

Classless networks enable the use of IP addresses with different subnet masks in the same network to enable efficient use of IP addresses

u said that " Classless networks enable the use of IP addresses with different subnet masks in the same network to enable efficient use of IP addresses"

but all the vlans u showd above have same subnet mask.

classful addressing has many limitations like only A,B,C are used for IP addressing

and so  total no of possible IP address are also restricted to much less than 2^32  

whereas since classless address dont divide it into classes so number of address spaces are maximum

and Deepthi_ts is female(mam)  not sir
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Why we need Classless =>  

If i need to buy a network with minimum host configuration, Let's say, a network with 16 IP.

so with already available network from  Class A,B,C. Class C can provide minimum network capacity that have 28 = 256 IP Possible.

but i need a network with 16 IP only, so what would i do with rest 256-16 = 240 this is nothing but simply 240 IP unused for me.

This is one reason behind Classless.

What is Classless =>    

as we know we have total no of IP available is  232 

so in classless initally they have not devided any prior fix network or block, you have to ask for a valid block range based on your need. (valid block means they have to follow certain rule to check you validness of your demand network or block range) so now exact #no of demand network or block is possible here .

This is a basic general level illustrations. 

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