Linux ifconfig Command

In the realm of Linux and network administration, managing network interfaces and configuring network settings is a fundamental task. The ifconfig (interface configuration) command is a powerful tool that allows users to view and configure network interfaces, IP addresses, subnets, and more. In this blog post, we will delve into the ifconfig command, exploring its syntax, options, practical applications, and understanding how it aids in managing network connectivity.

Basic Syntax

The basic syntax of the ifconfig command is straightforward:

bash
ifconfig interface options
  • interface: The name of the network interface.
  • options: Additional flags that modify the behavior of the ifconfig command.

Viewing Interface Information

To view information about all network interfaces, you can use the ifconfig command without any options. 

bash
ifconfig

This will display details about all active network interfaces, including their IP addresses, MAC addresses, and more.

Activating and Deactivating Interfaces

To activate a network interface, you can use the up option followed by the interface name.

bash
ifconfig eth0 up

To deactivate a network interface, you can use the down option followed by the interface name.

bash
ifconfig eth0 down

Assigning IP Address

To assign an IP address to a network interface, you can use the inet option followed by the IP address.

bash
ifconfig eth0 inet 192.168.1.100

Practical Applications

  1. Viewing Interface Information:

    bash
    ifconfig

  2. Activating an Interface:

    bash
    ifconfig eth0 up

  3. Assigning an IP Address:

    bash
    ifconfig eth0 inet 192.168.1.100

Understanding the Output

The output of the ifconfig command includes essential information about each network interface, such as its IP address, MAC address, subnet mask, and more. Understanding this information is crucial for configuring and managing network connectivity effectively.

Advanced Usage

Displaying a Specific Interface

To display information about a specific network interface, you can specify the interface name.

bash
ifconfig eth0

Setting Subnet Mask

You can set the subnet mask using the netmask option.

bash
ifconfig eth0 netmask 255.255.255.0

Assigning Multiple IP Addresses

You can assign multiple IP addresses to a single network interface using aliases. 

bash
ifconfig eth0:1 inet 192.168.1.101

This creates an alias eth0:1 with the specified IP address.