Whether you're configuring a server or troubleshooting a connection, knowing your subnet mask is key to understanding your network setup. Here are three reliable ways to find it on a Linux system.
Method 1: Using the ip Command
The ip command is a modern replacement for older networking tools and is widely supported across distributions.
Open a terminal window.
Run the command:
ip addr show
Locate your active network interface (typically eth0, wlan0, or similar).
Look for the inet entry, which will show your IP address in CIDR notation (e.g., 192.168.1.6/24).
The number after the slash (/24) represents the subnet mask.
/24 corresponds to 255.255.255.0, meaning the first 24 bits are reserved for the network portion.
If iproute2 is not installed, use your distribution’s package manager to install it:
Distribution Installation Command
Debian-based sudo apt install iproute2
Red Hat-based sudo dnf install iproute
Arch-based sudo pacman -S iproute2
openSUSE-based sudo zypper install iproute2
Method 2: Using the ifconfig Command
Though deprecated in many systems, ifconfig is still available and useful.
Open a terminal window.
Run the command:
ifconfig
Find your active interface. The subnet mask will be listed next to Mask (e.g., Mask:255.255.255.0).
If net-tools is missing, install it using:
Distribution Installation Command
Debian-based sudo apt install net-tools
Red Hat-based sudo dnf install net-tools
Arch-based sudo pacman -S net-tools
openSUSE-based sudo zypper install net-tools
Method 3: Using the nmcli Command
nmcli is the command-line interface for NetworkManager, commonly used in desktop environments.
Open a terminal window.
Run the command:
nmcli dev show
Look for the IP4.ADDRESS entry. The subnet mask will be shown in CIDR format (e.g., 192.168.1.5/24).
To install and activate NetworkManager:
Distribution Installation Command
Debian-based sudo apt install network-manager
Red Hat-based sudo dnf install NetworkManager
Arch-based sudo pacman -S networkmanager
openSUSE-based sudo zypper install NetworkManager
Then start and enable the service:
sudo systemctl start NetworkManager
sudo systemctl enable NetworkManager
With these methods, you can quickly identify your subnet mask and gain better control over your Linux network configuration. Whether you're using a desktop or server environment, these tools make the process simple and accessible.