Ifconfig

The Unix command ifconfig serves to configure and control TCP/IP network interfaces from a command line interface (CLI). The name ifconfig expresses the purpose of the command: an interface configurator. ifconfig originally appeared in 4.2BSD as part of the BSD TCP/IP suite — so in effect it formed part of the original internet toolkit. ["Linux Network Administrators Guide" [http://www.faqs.org/docs/linux_network/x-087-2-iface.interface.html Section 5.7. Interface Configuration for IP] ]

Common uses for ifconfig include setting an interface's IP address and netmask, and disabling or enabling a given interface. At boot time, many UNIX-style distributions initialize their network interfaces with shell-scripts that call ifconfig. ifconfig can also virtually a machine, functionally disconnecting it from a network.

Sample ifconfig output

The following screen-dialog shows the result of displaying the current state of a single active interface on two machines, eth0 on a Linux-based system and ural0 on OpenBSD.

eth0 Link enc
mtu 1500 lladdr 00:0d:0b:ed:84:fb media: IEEE802.11 DS2 mode 11b hostap (autoselect mode 11b hostap) status: active ieee80211: nwid ARK chan 11 bssid 00:0d:0b:ed:84:fb 100dBm inet 172.30.50.1 netmask 0xffffff00 broadcast 172.30.50.255 inet6 fe80::20d:bff:feed:84fb%ural0 prefixlen 64 scopeid 0xa

Current status

The free Berkeley Software Distribution UNIX operating systems (i.e. NetBSD, OpenBSD, and FreeBSD) continue active development of ifconfig and extension of its functionality to cover the configuration of wireless networking interfaces.

In Linux distributions based on 2.2.x Linux kernels, ifconfig, ipchains, and the route command operated together to connect a computer to a network, to define routes between networks, and to configure firewalls. ifconfig is sometimes stored in the /sbin directory. Distributions based on later kernels have deprecated ifconfig, route, and ipchains, replacing them with iptables and iproute2. iproute2 includes support for all that ifconfig(8) and route(8) do, as well as traffic-control (such as bandwidth-shaping).

Related tools

Versions of Microsoft Windows from Windows 95 to Windows Me used winipcfg to give a graphical display of current IP information. ipconfig, a command similar to ifconfig, comes with Microsoft operating-systems based on the Windows NT kernel. ipconfig also controls the Windows DHCP client. In Mac OS X, the ifconfig command functions as a wrapper to the IPConfiguration agent, and can control the BootP and DHCP clients from the command-line. Use of ifconfig to modify network settings in Mac OS X is discouraged, because ifconfig operates below the level of the system frameworks which help manage network configuration. To change network settings in Mac OS X from the command line, use /usr/sbin/ipconfig or /usr/sbin/networksetup.

iwconfig (one of the "Wireless tools for Linux"), which took its name from ifconfig, manages wireless network interfaces outside the original scope of Linux's ifconfig. iwconfig sets such specialized settings as a wireless network's SSID and WEP keys, and functions in tandem with iwlist. Linux also features iwspy, to read the signal, noise and quality of a wireless connection. wicontrol and iwiconfig perform similar functions for the BSDs. However OpenBSD has largely merged this functionality into ifconfig.

Other related tools for configuring Ethernet adapters are: ethtool, mii-tool, and mii-diag for Linux and show-link for Solaris.

and

ip - show / manipulate routing, devices, policy routing and tunnels

External links

* [http://linux.die.net/man/8/ifconfig ifconfig(8)] , manpage for the Linux net-tools ifconfig
* [http://www.freebsd.org/cgi/man.cgi?query=ifconfig ifconfig(8)] , manpage for the FreeBSD ifconfig
* [http://www.openbsd.org/cgi-bin/man.cgi?query=ifconfig ifconfig(8)] , manpage for the OpenBSD ifconfig
* [http://docs.sun.com/app/docs/doc/816-5166/6mbb1kq3e?a=view ifconfig(1M)] , manpage for the Solaris 10 ifconfig
* [http://developer.apple.com/documentation/Darwin/Reference/ManPages/man8/ifconfig.8.html ifconfig(8)] , manpage for the Mac OS X ifconfig
* [http://developer.apple.com/documentation/Darwin/Reference/ManPages/man8/ipconfig.8.html ipconfig(8)] , manpage for the Mac OS X ipconfig
* [http://developer.apple.com/documentation/Darwin/Reference/ManPages/man8/networksetup.8.html networksetup(8)] , manpage for the Mac OS X networksetup
* [http://www.leastprivilege.com/UPDATEDIfconfigForWindows21.aspx ifconfig] for Windows
* [http://linux.die.net/man/8/ip ip] , manpage for the Linux command ip

References