Subnet

Computers use special numbers to talk.

These numbers are like home addresses. One big network can be split into smaller groups. These small groups are called subnets.

Each subnet has its own part of the address. This part tells the computer which group it is in. The other part identifies the specific computer.

Special tools called routers help move data. They act like borders between the subnets. If two computers have different group numbers, the router helps them talk.

This helps big groups of computers stay organized. It also helps them find things quickly. Subnetting makes the whole system work better.

Computers use numbers to talk to each other. These are called IP addresses. One big network can be split into smaller groups. This way of dividing a network is called subnetting.

An IP address has two main parts. The first part is the network prefix. This part shows which group a computer belongs to. The second part is the host identifier. This part identifies a specific device. All computers in the same subnet have the same prefix.

How do we find the prefix? We use a tool called a subnet mask. The mask tells the computer where the prefix ends. In the modern way, we use CIDR notation. This uses a slash and a number to show the prefix length. For example, /24 means the first 24 bits are the prefix.

Special computers called routers help move data. A router acts like a border between subnets. If two computers have different prefixes, the router moves the data. This helps big networks stay organized. It also helps data move more quickly. Subnetting makes using addresses more efficient.

Computers on the internet need a way to find each other. They use special numbers called IP addresses to do this. A subnet, or subnetwork, is a way to divide one big network into smaller pieces. This process is called subnetting.

Dividing a network helps it stay organized. It also makes it easier to manage many different devices. Large organizations use subnets to keep their many parts running smoothly.

Every IP address is split into two logical parts. The first part is the routing prefix, which shows the network number. The second part is the host identifier, which identifies a specific device.

Computers in the same subnet always share the same prefix. To find this prefix, computers use a subnet mask. The mask is a string of bits used to separate the network part from the host part. In IPv4, this mask is often written in dot-decimal notation, like 255.255.255.0.

People have used different ways to manage these addresses over time. In the past, computers used classful networking. This meant the prefix was determined by the highest bits in the address. This system used classes named A, B, and C. Later, a better system called CIDR was introduced. CIDR stands for Classless Inter-Domain Routing. It is the modern standard used for both IPv4 and IPv6.

There are many specific rules for how these addresses work. An IPv4 address is made of 32 bits. An IPv6 address is much larger with 128 bits. Since 2006, IPv6 has been used more often because it has a huge amount of addresses.

In IPv4, a network might use CIDR notation to show its prefix. For example, /24 means the first 24 bits are the network prefix. This leaves 8 bits for the hosts. A network with 8 host bits can have 254 usable addresses. This is because the first and last addresses are reserved for special jobs.

Subnets work together like a giant tree or a mesh. Special computers called routers act as the borders between these subnets.

If two computers have different prefixes, the router moves the data between them. If they have the same prefix, the data stays on the local network. This is just like how mail moves between different towns. A router helps the data find the right path to its destination. This makes the whole internet much more efficient.

A subnet, or subnetwork, is a logical subdivision of an IP network. The process of dividing a larger network into two or more smaller networks is called subnetting. This practice is essential for organizing how data moves across the digital world. By creating subnets, administrators can manage large networks more effectively. They can also improve routing efficiency within a large organization. Subnetting allows a single network to be partitioned into a hierarchical tree-like structure or even a mesh.

Every IP address is divided into two logical fields. The first field is the routing prefix, which represents the network number. The second field is the host identifier, which identifies a specific device or interface. All computers belonging to the same subnet share an identical group of most-significant bits in their addresses. This shared prefix tells the network which group a device belongs to. The host identifier then provides a unique local identity for that specific device. This structure allows for precise addressing across different parts of a network.

In IPv4, a network is often characterized by a subnet mask, also known as a netmask. A subnet mask is a bitmask used to separate the prefix from the host identifier. It consists of a sequence of ones followed by a block of zeros. When a computer performs a bitwise AND operation using the IP address and the subnet mask, the result is the routing prefix. For example, if an IPv4 address uses a mask of 255.255.255.0, the first 24 bits are the prefix. The remaining 8 bits are reserved for host addressing.

Modern networks use Classless Inter-Domain Routing, or CIDR, to specify these prefixes. CIDR notation is written as the network address followed by a slash and the bit-length of the prefix. For instance, the notation 192.0.2.0/24 indicates a prefix of 24 bits. This method replaced the older classful networking system. In the classful system, the network prefix was determined by the highest-order bit sequence. This categorized addresses into Classes A, B, and C. CIDR provides much more flexibility in how address space is allocated.

Subnetting involves designating some high-order bits from the host part as part of the network prefix. This action adjusts the subnet mask and divides the network into smaller pieces. The number of available subnets can be calculated as 2 raised to the power of n, where n is the number of bits used for the network portion. The number of available hosts is calculated as 2 raised to the power of h, minus 2, where h is the number of host bits. The subtraction of two accounts for the reserved network and broadcast addresses. For example, a subnet with 6 host bits allows for 62 usable host combinations.

Traffic moves between subnets using special gateway computers called routers. A router serves as a logical or physical boundary between different subnets. When a router compares the source and destination addresses, it looks at their routing prefixes. If the prefixes differ, the router must exchange the traffic between the subnets. If the prefixes are the same, the data can be sent directly to the target host on the local network. This process ensures that data finds the most efficient path to its destination.

There are different standards for different types of Internet Protocol. IPv4 uses 32-bit addresses, while its successor, IPv6, uses 128-bit addresses. IPv6 has been increasingly deployed since approximately 2006. Because the IPv6 address space is so massive, containing 2^128 addresses, the need to conserve space is not a limiting factor. In IPv6, the routing prefix is typically 32 bits. While IPv4 relies heavily on subnet masks for on-link determination, IPv6 uses the Neighbor Discovery Protocol (NDP). This distinction highlights how different generations of technology handle network organization.