What Is Subnetting And Supernetting?

When class B addresses are used by class C subnet mask then the result we get is known as subnets. There are many reasons for which we create subnets of an IP network. The basic purpose of subnet is to control traffic over networks.
To get the network and node parts of an address, we apply subnet mask to an IP address. 1 represents to network bit and 0 represents to node bit. To get the network address, we apply an operation among the IP address and the subnet mask is known as Bitwise Logical (AND).

Super-netting is also known as Classes Inter-Domain Routing. The way through which multiple internet addresses of a class are combined together is known as Super-netting. Suppose we have two network addresses. One is 192.168.3.0/18 and other is 192.168.4.0/18. By using Super-netting, we can combine these two addresses into a single address as 192.168.3.0/17. Here seventeen (17) is showing that first 17 bits are representing the network part of address (192.168.3.0/17). There are some protocols which are used Super-netting including BGP and OSPF. Here BGP is known as Border Gateway Protocol and OSPF is known as Open Shortest Path First and it a s routing protocol.

CIDR -- Classless InterDomain Routing. CIDR was invented several years ago to keep the internet from running out of IP addresses. The "classful" system of allocating IP addresses can be very wasteful; anyone who could reasonably show a need for more that 254 host addresses was given a Class B address block of 65533 host addresses. Even more wasteful were companies and organizations that were allocated Class A address blocks, which contain over 16 Million host addresses! Only a tiny percentage of the allocated Class A and Class B address space has ever been actually assigned to a host computer on the Internet.
People realized that addresses could be conserved if the class system was eliminated. By accurately allocating only the amount of address space that was actually needed, the address space crisis could be avoided for many years. This was first proposed in 1992 as a scheme called Supernetting. Under supernetting, the classful subnet masks are extended so that a network address and subnet mask could, for example, specify multiple Class C subnets with one address. For example, If I needed about 1000 addresses, I could supernet 4 Class C networks together:
192.60.128.0   (11000000.00111100.10000000.00000000)  Class C subnet address
192.60.129.0   (11000000.00111100.10000001.00000000)  Class C subnet address
192.60.130.0   (11000000.00111100.10000010.00000000)  Class C subnet address
192.60.131.0   (11000000.00111100.10000011.00000000)  Class C subnet address
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192.60.128.0   (11000000.00111100.10000000.00000000)  Supernetted Subnet address
255.255.252.0  (11111111.11111111.11111100.00000000)  Subnet Mask
192.60.131.255 (11000000.00111100.10000011.11111111)  Broadcast address
In this example, the subnet 192.60.128.0 includes all the addresses from 192.60.128.0 to 192.60.131.255. As you can see in the binary representation of the subnet mask, the Network portion of the address is 22 bits long, and the host portion is 10 bits long.
Under CIDR, the subnet mask notation is reduced to a simplified shorthand. Instead of spelling out the bits of the subnet mask, it is simply listed as the number of 1s bits that start the mask. In the above example, instead of writing the address and subnet mask as
192.60.128.0, Subnet Mask 255.255.252.0
the network address would be written simply as:
192.60.128.0/22 which indicates starting address of the network, and number of 1s bits (22) in the network portion of the address. If you look at the subnet mask in binary (11111111.11111111.11111100.00000000), you can easily see how this notation works.
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Source:
Becker, R. (2009, april 8). IP Subnetting Tutorial. Retrieved april 8, 2009, from www.ralphb.net www.ralphb.net