As the web grew, the initial Classful addressing scheme became a limitation. The IP address space had been exhausted because all networks had to select one of three feasible sizes. Many addresses had been unused.
Two fresh mechanisms were invented to overcome the restrictions, which are as
follows:
• Subnet addressing
• Classless addressing
Of having three distinct address classes instead, permit the division between prefix and suffix that occurs on an arbitrary boundary. The classless addressing scheme solves the issue by allowing an ISP to assign a prefix that's, 28 bits long (14 hosts are allowed).
SUBNET/ADDRESS MASK:
How can an Ip be divided in an arbitrary boundary? To employ a classless or subnet address, the table inside routers and hosts which contain address must preserve two pieces of info with each address: the 32-bit address itself and another 32-bit value that specifies the boundary that is called the Address Subnet or Mask.
Suppose
D = Destination Address
(A, M)= (32-bit IP, 32-bit Address Mask)
A = = (D & M)
Now for example look at a 32-bit mask:
11111111 00000000
Which can be denoted in dotted decimal mainly because 255.255.0.0
Consider a network prefix:
10000000 00001010 00000000
Which may be denoted in dotted decimal worth as 128.10.0.0.
Look at a destination address: 128.10.2.3
Which has Binary equivalent as:
10000000 00001010 00000010 00000011
A logical ‘and’ between D and M makes the binary result as:
10000000 00001010 00000000
Which is add up to prefix 128.10.0.0
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