root

Jun 11 2026

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What You'll Learn

How to use Nmap — the industry-standard network scanner — to discover devices and open ports.

⚠️ Important: Only scan networks and systems you own or have explicit permission to test. Unauthorized scanning is illegal.

Prerequisites

• A computer on a local network (home or lab)
• Admin/root privileges

Step 1 — Install Nmap

macOS:

brew install nmap

Ubuntu/Debian:

sudo apt update && sudo apt install nmap -y

Windows: Download the installer from nmap.org

Step 2 — Find Your Network Range

# macOS / Linux — find your IP address
ifconfig | grep "inet "

# Windows
ipconfig

If your IP is 192.168.1.45, your network range is likely 192.168.1.0/24.

Step 3 — Run Your First Scan

# Discover all live devices on your network
nmap -sn 192.168.1.0/24

This "ping scan" shows which hosts are online without probing ports.

Step 4 — Scan Open Ports on a Device

# Replace with a target IP from the previous scan
nmap 192.168.1.1

Understanding the output:

Column	Meaning
PORT	Port number and protocol
STATE	open / closed / filtered
SERVICE	What service typically runs here

Step 5 — A More Detailed Scan

# Detect OS and service versions (requires root/admin)
sudo nmap -A 192.168.1.1

Well done!

You've performed your first network reconnaissance — a core skill in both offensive and defensive security.

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