Subnetting

Subnetting is the process of dividing a large IP network into multiple smaller networks, called subnets.

Subnetting improves network organization, security, and routing efficiency.

Without subnetting, every device would belong to one large network.

As networks grow, this causes:

• More broadcast traffic
• Reduced performance
• Difficult management
• Poor security

Subnetting divides a network into smaller, more manageable sections.

Suppose a company owns the network:

192.168.1.0/24

Instead of placing all devices into one network, it can create several subnets.

Example:

Office A

192.168.1.0/26

Office B

192.168.1.64/26

Office C

192.168.1.128/26

Office D

192.168.1.192/26

Each subnet functions as an independent network.

A subnet is a group of devices that share the same network prefix.

Devices within the same subnet can usually communicate directly.

Communication between different subnets normally passes through a router.

Subnet A
192.168.1.0/26
        │
        ▼
      Router
        ▲
        │
Subnet B
192.168.1.64/26

Every IP address contains two parts:

• Network portion
• Host portion

Example:

192.168.1.25/24

Network

192.168.1

Host

25

The prefix length determines how many bits belong to the network.

Historically, subnetting was expressed using a subnet mask.

Example:

255.255.255.0

Today, CIDR notation is more common.

Example:

/24

Both represent the same network.

CIDR (Classless Inter-Domain Routing) indicates how many bits belong to the network portion.

Examples:

See:

CIDR Notation

Subnetting provides several advantages.

• Reduces broadcast traffic
• Improves network performance
• Simplifies administration
• Enhances security
• Makes efficient use of IP addresses
• Improves routing efficiency

Subnetting is used in both IPv4 and IPv6.

IPv6 typically uses much larger network prefixes, commonly:

/64

for local networks.

No.

A small home network usually uses a single subnet.

Larger organizations commonly divide their networks into many subnets.

Examples:

• Offices
• Departments
• Data centers
• Guest Wi-Fi
• Server networks

Several Telenegar tools use subnet information.

• IP Check
• Subnet Calculator

Subnet Calculator can help determine:

• Network address
• Broadcast address (IPv4)
• First usable host
• Last usable host
• Number of hosts
• CIDR notation
• Subnet mask

• Subnetting changes an IP address.
  • False. It changes how the address is interpreted.

• Every subnet must contain 254 hosts.
  • False. The number of hosts depends on the subnet size.

• Subnetting is only used on large enterprise networks.
  • False. Even many home and small business networks use subnetting.

• IP Addresses
• IPv4
• CIDR Notation
• Default Gateway
• Subnet Calculator

subnet subnetting cidr ipv4 ipv6 networking