ifconfig - Linux

Overview

ifconfig (interface configurator) is a traditional command-line tool used to configure the network interfaces in Unix-based operating systems. It allows users to view and modify parameters associated with networking, such as enabling/disabling interfaces or setting up IP addresses. This command is instrumental in diagnosing network issues and configuring network settings.

Syntax

The general syntax of ifconfig is as follows:

ifconfig [interface]
ifconfig [interface] [options] [address]
  • interface: The name of the network interface you want to configure (e.g., eth0, wlan0).
  • options: Commands to manipulate the interface settings.
  • address: The IP address or other parameters to assign to the interface.

Options/Flags

Here are some commonly used options and flags in ifconfig:

  • up: Activates an interface.
  • down: Deactivates an interface.
  • addr: Sets the IP address of the interface.
  • netmask <mask>: Sets the subnet mask.
  • broadcast <address>: Sets the broadcast address.

Example Usage:

ifconfig eth0 up

This command activates the eth0 interface.

Examples

  • View All Interfaces:

    ifconfig -a

    This displays all the available network interfaces, including those that are down.

  • Set an IP Address:

    ifconfig eth0 192.168.1.100 netmask 255.255.255.0

    This assigns the IP address 192.168.1.100 to eth0 with a subnet mask of 255.255.255.0.

  • Enable and Disable Interface:

    ifconfig eth0 up
ifconfig eth0 down

    These commands activate and deactivate the eth0 interface, respectively.

Common Issues

  • Interface Not Found: If you get an error saying the interface does not exist, double-check the interface name.
  • Permissions: ifconfig typically requires root access. Use sudo ifconfig if you encounter permission denied errors.

Integration

ifconfig can be combined with other tools like grep for more effective results:

ifconfig | grep "inet "

This command filters and shows only lines containing IP addresses.

  • ip: A modern replacement for ifconfig that provides more detailed and extensive network management capabilities.
  • netstat: Displays network connections, routing tables, and statistics.
  • iwconfig: Similar to ifconfig, but dedicated to wireless network interfaces.

For thorough documentation, please consult the manual pages (man ifconfig on your terminal) or the official Linux documentation online.