Subnet
- A subnetwork or subnet is a logical subdivision of an IP network.
- The practice of dividing a network into two or more networks is called subnetting.
- Subnetting improve network security and performance.
- Computers that belong to a subnet are addressed with a common, identical, most-significant bit group in their IP address.
- The IP address divided into two fields, a network or routing prefix and the rest field or host identifier.
Subnet mask
- A subnet mask is 32-bit data used for bitwise operations on a network of IP addresses that has been divided into two or more groups.
- Subnet masks are used to design subnetworks or subnets, that connect local networks.
- It determines both the number and size of subnets where the size of a subnet is the number of hosts that can be addressed.
- A subnet mask neither works like an IP address, nor does it exist independently from them.
- A subnet mask can create setting all subsequent network bits to "1" and host bits to "0".
Dotted Decimal Representation of Subnet Masks
- Subnet masks are frequently expressed in dotted decimal notation.
- After the bits are set for the network ID and host ID portion, the resulting 32-bit number is converted to dotted decimal notation. But it is not a IP address.
Network Prefix Length Representation of Subnet Masks
- Because the network ID bits must always be chosen in a contiguous fashion from the high order bits, a shorthand way of expressing a subnet mask is to denote the number of bits that define the network ID as a network prefix using the network prefix notation: "/".
Advantages
- It reduces network traffic by removing collision and broadcast traffic, that overall improve performance.
- Subnetting breaks large network in smaller networks and smaller networks are easier to manage.
- Facilitated spanning of large geographical distances.
- Prevents unnecessary broadcasts.
- Subnetting allows you to save money by reducing requirement for IP range.
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