Ifconfig

ifconfig (short for interface config) is a system administration utility in Unix-like operating systems for network interface configuration.

The utility is a command-line interface tool and is also used in the system startup scripts of many operating systems. It has features for configuring, controlling, and querying TCP/IP network interface parameters. Ifconfig originally appeared in 4.2BSD as part of the BSD TCP/IP suite.

Many Linux distributions have deprecated ifconfig in favor of tools from iproute2.

Common uses for ifconfig include setting the IP address and subnet mask of a network interface and disabling or enabling an interface. At boot time, many Unix-like operating systems initialize their network interfaces with shell scripts that call ifconfig. As an interactive tool, system administrators routinely use the utility to display and analyze network interface parameters. The following two examples show the output of the tool when querying the state of a single active interface each on a Linux-based host (interface eth0) and the ural0 interface on an OpenBSD installation.

ifconfig is also commonly used to change the medium access control (MAC) address of an interface. In this process, the network interface is first disabled (set down) with the ifconfig command, followed by a MAC change command:

The Berkeley Software Distribution UNIX operating systems (e.g., NetBSD, OpenBSD, and FreeBSD) continue active development of ifconfig and extension of its functionality to cover the configuration of wireless networking interfaces, VLAN trunking, controlling hardware features such as TSO or hardware checksumming or setting up bridge and tunnel interfaces. Solaris has historically used ifconfig for all network interface configuration, but as of Solaris 10 introduced dladm to perform data-link (OSI model layer 2) configuration, reducing ifconfig's purview to IP configuration.

In older Linux distributions, ifconfig, in conjunction with the utility route, was used to connect a computer to a network, and to define routes between networks. ifconfig for Linux is part of the package net-tools, released as the latest version 2.10 on 7 January 2021.

Many Linux distributions have deprecated the use of ifconfig and route in favor of the software suite iproute2, such as ArchLinux or RHEL since version 7, which has been available since 1999 for Linux 2.2. iproute2 includes support for all common functions of ifconfig(8), route(8), arp(8) and netstat(1). It also includes multicast configuration support, tunnel and virtual link management, traffic control, and low-level IPsec configuration, among other features.