How to scan your network for unknown devices

Complete guide with multiple methods and troubleshooting

7-10 min read
Expert Verified
Last Updated: August 2025

Quick Answer

To scan your network for unknown devices, you can use various methods including built-in tools like Command Prompt or PowerShell, as well as third-party applications. Each method allows you to identify devices connected to your network, helping to enhance security and manage network resources effectively.

Medium⏱ 7-10 min read

Prerequisites & Requirements

Before starting the network scan, ensure you have the following:
  • •A computer running Windows 10, Windows 11, macOS, or a Linux distribution.
  • •Administrator access to your device and network router.
  • •Network scanning tools like Nmap or Advanced IP Scanner installed (if using third-party tools).
  • •Backup any important data as a precaution before making changes to network settings.

Method 1: Using Command Prompt

This method is effective for users who prefer built-in tools and command-line interfaces. It allows you to quickly identify devices on your network using ARP and ping commands.
  • •Step 1: Press `Windows + R` to open the Run dialog. Type `cmd` and press `Enter` to open Command Prompt.
  • •Step 2: In the Command Prompt window, type `arp -a` and press `Enter`. This command will display a list of all devices currently connected to your network.
  • •Step 3: Review the list of IP addresses and MAC addresses to identify unknown devices.
  • •Step 4: If no devices appear, ensure your computer is connected to the network and repeat the command.

For Windows 11

Windows 11 users can follow the same steps as above, but may also access Command Prompt through the Start menu.
  • •Click on the Start button, type `Command Prompt`, and select it from the search results.

For Windows 10

Windows 10 users can also access Command Prompt via the Start menu.
  • •Click on the Start button, type `cmd`, right-click on Command Prompt, and select `Run as administrator`.

Method 2: Using Nmap

Nmap is a powerful network scanning tool that provides detailed information about devices on your network. This method is ideal for users who need more comprehensive data.
  • •Step 1: Download and install Nmap from the official website: https://nmap.org/download.html.
  • •Step 2: Open Nmap and enter the command `nmap -sn 192.168.1.0/24` (replace with your network's IP range) in the terminal or command line interface.
  • •Step 3: Press `Enter` to execute the scan. Nmap will display a list of devices, including their IP addresses, MAC addresses, and device types.
  • •Step 4: Review the results to identify any unknown devices.

Troubleshooting Common Issues

If you encounter issues while scanning your network, consider the following solutions:
  • •Error: 'No devices found' - Solution: Ensure your device is connected to the network and try running the command again.
  • •Issue: Nmap fails to run - Fix: Verify that Nmap is installed correctly and that you have the necessary permissions.
  • •Problem: Incomplete device list - Workaround: Check your router settings to ensure that device discovery is enabled.

Advanced Tips & Shortcuts

For power users looking to optimize their network scanning process, consider these tips:
  • •Keyboard shortcut: `Ctrl + Shift + Esc` - Opens Task Manager quickly to monitor network usage.
  • •Command line: `ping 192.168.1.255` - Sends a ping to the broadcast address to discover devices.
  • •Hidden feature: Nmap's `-O` option - Enables OS detection for more detailed device information.

Common Mistakes to Avoid

Avoid these common pitfalls:

Expert Tips

For the best results, regularly monitor your network and update your scanning tools to ensure compatibility with new devices.