Ifconfig

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The correct title of this article is ifconfig. The initial letter is shown capitalized due to technical restrictions.
Sample output from ifconfig on Linux
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Sample output from ifconfig on Linux

The Unix command ifconfig can function as a tool to configure a network interface for TCP/IP from the command line interface (CLI). The name ifconfig expresses the purpose of the command: an interface configurator. [1]

ifconfig originally appeared as part of the BSD TCP/IP suite — so in effect it formed part of the original internet toolkit. The ifconfig command first appeared in 4.2BSD.

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[edit] Functionality

Common uses for ifconfig include setting an interface's IP address and netmask, and bringing an interface up or down. Network administrators can also use ifconfig to tweak several other settings on the interface.

In this way the ifconfig command operates in conjunction with other tools to assign and manage IP addresses and interfaces on LANs, wide-area networks (WANs), and the Internet. ifconfig can also virtually airwall a machine, that is, functionally disconnect it from a network.

[edit] Sample ifconfig output

The following screen-dialog shows the result of displaying the current state of a single active ("up") interface (eth0) on a machine:

$ /sbin/ifconfig
eth0      Link encap:Ethernet  HWaddr 00:0F:20:CF:8B:42
          inet addr:217.149.127.10  Bcast:217.149.127.63  Mask:255.255.255.192
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:2472694671 errors:1 dropped:0 overruns:0 frame:0
          TX packets:44641779 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:1761467179 (1679.8 Mb)  TX bytes:2870928587 (2737.9 Mb)
          Interrupt:28


[edit] 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. Distributions based on later kernels have deprecated ifconfig, route, and ipchains, replacing them to large extent 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).

[edit] Related tools

Early builds 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.

iwconfig, which took its name from ifconfig, manages wireless network interfaces that Linux's ifconfig command could not handle. It can set such specialized settings as a wireless network's SSID and WEP keys, and functions in tandem with iwlist.

[edit] External links

[edit] References

  1. ^ Linux Network Administrators Guide Section 5.7. Interface Configuration for IP
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