Sometimes you need to find out which devices are connected to your network. There may be several reasons for this. Your Internet may be slower than usual, you may notice suspicious activity related to someone stealing your Wi-Fi, or you may solve the problem. Whatever the reason, it is recommended that you check who else is connected to your network so that you can take appropriate action.
Nmap is a great tool to help you find devices connected to your network. This is an open source network research tool that tells you which other systems are on your network, as well as their IP addresses, what services they provide, which version of the operating system they use, and much more. It works on almost all major operating systems, including Linux, Windows, and Mac OS.
In this article, we’ll show you how to install and use Nmap to search for devices connected to your Internet.
We will use Debian10 to describe the procedure mentioned in this article. You can use the same procedure for older versions of Debian.
Step 1: Open Debian Terminal
Launch the terminal application on your system by going to activity tab in the upper left corner of the Debian desktop. Then in the search bar enter Terminal, When the terminal icon appears, click on it to launch it.
Step 2: Install Nmap Network Scan Tool
Now in the Terminal application, run the following command on behalf of sudo to install the Nmap network scan tool.
$ sudo apt-get install nmap
When prompted for a password, enter the sudo password.
System will provide you g / l ability to confirm installation. Click Y confirm and wait a while until the installation is completed on your system.
Step 3: Get the IP Range / Subnet Mask of Your Network
Nmap requires a network ID to scan a connected device on a specific network. Thus, to find the network ID, we need our IP address and subnet mask.
Run the command below in Terminal to find the IP address and subnet mask of your system:
$ ip a
The above output indicates that our system uses the IP address 192.168.72.164 / 24. / 24 indicates that our subnet mask is 255.255.255.0. This means that our network identifier is 192.168.72.0 and the network range is from 192.168.72.1 to 192.168.72.255.
(Note. The network ID is calculated by performing the AND operation for the IP address and subnet mask. If you do not know how to perform the AND operation, you can use any online subnet calculator).
Step 4. Scan the network for connected devices using Nmap
Now that we have the network ID, run Nmap scan with -sn option using the following syntax:
$ nmap –sn
In our scenario, it will be:
$ nmap -sn 192.168.72.0/24
Using nmap with -sn the option does not scan ports, it only returns a list of active hosts:
The above results show that three active devices are connected to our network, including our system (192.168.72.164)
That is all there is to it! We learned how to find connected devices connected to the network using the Nmap tool. This can help you determine which unwanted users are connected and are using your network bandwidth.
How to find devices connected to your network using Debian Linux