🔢 Advanced Subnet Calculator

Professional IP subnetting calculator in your terminal. Fast, accurate, and beautiful.

Install

curl -sSL https://raw.githubusercontent.com/mikegilkim/subnet-calculator/main/install.sh | sudo bash

Usage

Interactive Mode:

subnet

Direct Calculation:

subnet 192.168.1.0/24
subnet 10.0.0.0/8
subnet 172.16.0.0/16

Features

📊 Complete Network Information

• Network address and broadcast address
• Subnet mask and wildcard mask
• CIDR notation
• Usable IP range (first and last)
• Total IPs and usable hosts

🎯 IP Analysis

• IP Class Detection (A, B, C, D, E)
• IP Type (Private vs Public)
• Identifies RFC1918 private ranges

🔢 Multiple Representations

• Decimal - Standard dotted notation
• Binary - 8-bit octet format
• Hexadecimal - For network programming

📋 Subnet Division

• Shows how to divide into smaller subnets
• Lists up to 8 example subnets
• Includes usable ranges for each

📖 Quick Reference Table

• Common CIDR notations (/24 to /32)
• Subnet masks for each
• Total IPs and usable hosts

Screenshot

╔══════════════════════════════════════════════════════════════════════════════╗
║                      SUBNET CALCULATOR RESULTS                               ║
╚══════════════════════════════════════════════════════════════════════════════╝

▶ INPUT
────────────────────────────────────────────────────────────────────────────────
  IP Address / CIDR:        192.168.1.0/24

▶ IP ADDRESS INFORMATION
────────────────────────────────────────────────────────────────────────────────
  IP Class:                 C (Small Networks)
  IP Type:                  Yes (192.168.0.0/16)

▶ NETWORK INFORMATION
────────────────────────────────────────────────────────────────────────────────
  Network Address:          192.168.1.0
  Broadcast Address:        192.168.1.255
  Subnet Mask:              255.255.255.0
  Wildcard Mask:            0.0.0.255
  CIDR Notation:            /24

▶ USABLE IP RANGE
────────────────────────────────────────────────────────────────────────────────
  First Usable IP:          192.168.1.1
  Last Usable IP:           192.168.1.254
  Total IP Addresses:       256
  Usable Hosts:             254

▶ BINARY REPRESENTATION
────────────────────────────────────────────────────────────────────────────────
  IP Address (Binary):      11000000.10101000.00000001.00000000
  Subnet Mask (Binary):     11111111.11111111.11111111.00000000
  Network Address (Binary): 11000000.10101000.00000001.00000000

▶ SUBNET DIVISION EXAMPLES
────────────────────────────────────────────────────────────────────────────────
  Divide /24 into /25 subnets:

  Subnet 1: 192.168.1.0/25
    Range: 192.168.1.1 - 192.168.1.126

  Subnet 2: 192.168.1.128/25
    Range: 192.168.1.129 - 192.168.1.254

Use Cases

Perfect for:

• 🌐 Network Engineers - Plan subnet allocations
• 🎓 Students - Learn subnetting concepts
• 🔧 System Administrators - Quick network calculations
• 📝 CCNA/Network+ Prep - Practice subnetting
• 🏢 IT Professionals - Network design and troubleshooting

Requirements

• Linux (Ubuntu, Debian, CentOS, RHEL, Arch)
• Bash 4.0+
• bc (auto-installed)

Examples

Calculate Class C Network

subnet 192.168.1.0/24

Shows 256 total IPs, 254 usable hosts

Calculate Class A Network

subnet 10.0.0.0/8

Shows 16,777,216 total IPs

Calculate Small Subnet

subnet 192.168.1.0/30

Shows point-to-point links (2 usable hosts)

Calculate Single Host

subnet 192.168.1.1/32

Shows single host subnet

Manual Install

wget https://raw.githubusercontent.com/mikegilkim/subnet-calculator/main/subnet-calc.sh
chmod +x subnet-calc.sh
sudo mv subnet-calc.sh /usr/local/bin/subnet-calc
echo "alias subnet='/usr/local/bin/subnet-calc'" >> ~/.bashrc
source ~/.bashrc

Understanding the Output

Network Address

The first address in the subnet. Cannot be assigned to hosts.

Broadcast Address

The last address in the subnet. Used to send messages to all hosts.

Usable IP Range

IPs between network and broadcast that can be assigned to devices.

Subnet Mask

Defines which portion of IP is network vs host.

Wildcard Mask

Inverse of subnet mask. Used in access control lists (ACLs).

CIDR Notation

Compact way to represent subnet mask (/24 = 255.255.255.0).

Common CIDR Notations

CIDR	Subnet Mask	Usable Hosts	Common Use
/8	255.0.0.0	16,777,214	Large enterprise
/16	255.255.0.0	65,534	Medium enterprise
/24	255.255.255.0	254	Small network
/25	255.255.255.128	126	Small subnet
/26	255.255.255.192	62	Smaller subnet
/27	255.255.255.224	30	Tiny subnet
/28	255.255.255.240	14	Very small
/29	255.255.255.248	6	Point-to-multipoint
/30	255.255.255.252	2	Point-to-point
/31	255.255.255.254	2	Point-to-point (RFC3021)
/32	255.255.255.255	1	Single host

Private IP Ranges (RFC1918)

• 10.0.0.0/8 - 10.0.0.0 to 10.255.255.255
• 172.16.0.0/12 - 172.16.0.0 to 172.31.255.255
• 192.168.0.0/16 - 192.168.0.0 to 192.168.255.255

Tips & Tricks

Quick Class C Subnetting:

subnet 192.168.1.0/24   # 254 hosts
subnet 192.168.1.0/25   # 126 hosts (2 subnets)
subnet 192.168.1.0/26   # 62 hosts (4 subnets)
subnet 192.168.1.0/27   # 30 hosts (8 subnets)

Point-to-Point Links:

subnet 10.0.0.0/30      # 2 usable IPs for router links

Verify Your Network Design:

subnet 172.16.0.0/22    # Check if your allocation fits

Troubleshooting

"bc: command not found"

sudo apt install bc -y

"Permission denied"

sudo subnet 192.168.1.0/24

"Invalid IP address"

• Check format: must be X.X.X.X/Y
• Octets must be 0-255
• CIDR must be 0-32

License

MIT - Use freely, modify as needed.

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