How to Use the Linux ifconfig Command

The ifconfig or Interface configuration is a network configuration utility in Linux and other Unix-like systems that allows us to configure, control, and query TCP/IP network interfaces from the command-line.

Using the ifconfig command, we can perform an array of network administration operations such as enabling and disabling interfaces, managing ARP cache, managing network routes, and more.

In this tutorial, we will explore how we can work with the ifconfig command in Linux to perform various network tasks in our Linux systems.

How to Install ifconfig

The ifconfig command has become deprecated and has been superseded by the ip command which provides more functionality and performance. This means that it may not be installed by default on your target machine.

You can check if the command is installed by invoking the command:

ifconfig

If the command is not installed, you will get command not found error:

Command 'ifconfig' not found, but can be installed with:

Installing ifconfig on Debian-Based Distro

If you are using any Debian-based distribution, you can install the ifconfig utility as shown in the command below:

sudo apt-get install net-tools -y

Installing ifconfig on Rocky Linux

If you are on any REHL based distribution, you can use dnf or yum commands as shown below:

sudo dnf install net-tools -y

Installing ifconfig on Arch

On any Arch-based distribution, you can use the command below to install ifconfig.

sudo pacman -S net-tools

How to use the ifconfig Command

Once you have the ifconfig installed, you can invoke it from the terminal to use it. The command syntax is as shown:

ifconfig [-v] interface [aftype] options | address

Where the:

1. interface - refers to the name of the network interface you wish to manage.
2. address - refers to the IP address you wish to assign.

Ifconfig Show Network Interface Information

If you run the ifconfig command without any arguments, it should return information about all the network interfaces in your system. This will include information such as the IP address (IPv4 and IPv6), Mac Address, and more.

ifconfig

Example output:

eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.227.84  netmask 255.255.240.0  broadcast 192.168.239.255
        inet6 fe80::215:5dff:fe2a:2889  prefixlen 64  scopeid 0x20<link>
        ether 00:15:5d:2a:28:89  txqueuelen 1000  (Ethernet)
        RX packets 54993  bytes 79711020 (79.7 MB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 11259  bytes 832608 (832.6 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

To get the network information for a specific address, you can use the ifconfig followed by the name of the network interface. For example, to show network information for the interface eth0, you can run the command:

ifconfig eth0

Output:

eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.227.84  netmask 255.255.240.0  broadcast 192.168.239.255
        inet6 fe80::215:5dff:fe2a:2889  prefixlen 64  scopeid 0x20<link>
        ether 00:15:5d:2a:28:89  txqueuelen 1000  (Ethernet)
        RX packets 55021  bytes 79716280 (79.7 MB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 11259  bytes 832608 (832.6 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

Ifconfig Assign IP Address

You can also use the ifconfig command to assign a new IP address and netmask to a given network interface.

The syntax is as shown:

ifconfig [interface] [ip_address] netmask [subnet-mask]

For example, to assign a new IP address to the eth0 address, run the command:

ifconfig eth0 192.168.227.100 netmask 255.255.240.0

This should assign a new IP address to the eth0 interface.

Ifconfig Enable or Disable Network Interfaces

In some instances, you may need to enable or disable a given network interface.

To disable a given network interface, use the command syntax as shown:

sudo ifconfig [interface] down

For example, to disable the eth0 run:

sudo ifconfig eth0 down

To activate an inactive interface, run the command:

sudo ifconfig [interface] up

For example, run the command:

sudo ifconfig eth0 up

Configuring Monitor Mode

Modern network interfaces support monitor or promiscuous mode which allows you to capture and view network packets. Monitor mode is an essential feature in networking hacking.

To check the most popular network cards for hacking that support Monitor mode:

https://www.geekbits.io/best-wi-fi-hacking-adapters-in-2023/

To put a network in monitor mode using ifconfig run the command:

ifconfig [interface] promisc

To disable monitor mode, run the command:

ifconfig [interface] -promisc

Ifconfig Change Mac Address

https://www.geekbits.io/how-to-find-the-mac-address-of-network-interface-in-linux/

To change the Mac Address of a given network interface, use the command as shown:

ifconfig [interface] hw ether [mac_addres]

For example, to change the mac address of the eth0 interface, run:

ifconfig eth0 hw ether 00:15:5d:2a:28:89

Conclusion

In this post, we explored the workings of the ifconfig command in Linux to show information about network interfaces, configuring new addresses, configuring monitor mode, and more.

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