SUBNETTING

Subnetting is a technique that allows network administrators to take advantage of 32 bit IP addresses that are available more efficiently. Subnetting techniques to make the network more extensive scale and not by classes under IP (IP Classes) A, B, and C to the set. With subnetting, you can create a network with more realistic limits appropriate host necessary.Subnetting provide a more flexible way to determine which parts of a 32 bit IP adddress representing network ID and which part represents the host ID.

Classes with a standard IP address, only 3 possible network IDs are available; 8 bits for class A, 16 bits for class B, and 24 bits for class C. Subnetting allows you to choose a random bit number (arbitrary number) to be used as a network ID.

Two main reasons for doing subnetting :

1. Allocating the limited IP address to be more efficient. If the Internet is limited by the addresses in class A, B, and C, each network will possess 254, 65,000, or 16 million to the host device's IP address. Although there are many networks with the number of hosts more than 254, but only a few network (if you do not want to say no), which has hosted as many as 65,000 or 16 million. And the network has more than 254 devices will require the allocation of class B and will probably spend about 10 thousand useless IP address.
2. The second reason is, although an organization has thousands of host devices, operate all the devices within the same network ID will slow down the network. The way TCP / IP works arranged for all computers with the same network ID must be on the same physical network as well. Physical network has the same broadcast domain, which means a medium network must carry all traffic for the network. Due to performance reasons, networks are usually segmented into smaller broadcast domains - even less - of the Class C address.

Subnets

Subnet is a network within a network of other (Class A, B, and C). Subnets are created using one or more bits in the host Class A, B, or C to widen the network ID. If the default network ID is 8, 16, and 24 bits, then the subnet network ID can have a length that is different.