ifconfig command

ifconfig - configure a network interface

The ifconfig command in Linux is a traditional tool used to display and configure network interfaces (e.g., Ethernet, Wi-Fi). It shows details like IP addresses, MAC addresses, and interface status, and can enable, disable, or modify network settings. While newer systems prefer ip (from iproute2), ifconfig is still widely used on older systems or where net-tools is installed.

Note: ifconfig may not be installed by default on modern distros (e.g., Ubuntu 20.04+). Install it with sudo apt install net-tools or use ip addr instead.

Usage: ifconfig [-v] [-a] [-s] [interface] [options]

• interface: The network interface (e.g., eth0, wlan0; optional).
• options: Flags or parameters to configure the interface.

Common Options

Option/Action	Description
(no option)	List all active interfaces
up	Enable an interface
down	Disable an interface
netmask	Set subnet mask
hw ether	Set MAC address
-a	Show all interfaces (active or inactive)

Examples

• Basic Usage

  Run ifconfig without arguments to list all active network interfaces.

  ifconfig

  • Output (example):

    eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
          inet 192.168.1.100  netmask 255.255.255.0  broadcast 192.168.1.255
          ether 00:14:22:01:23:45  txqueuelen 1000  (Ethernet)
          RX packets 1234  bytes 567890 (567.8 KB)
          TX packets 567  bytes 123456 (123.4 KB)
    
    lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
          inet 127.0.0.1  netmask 255.0.0.0
          loop  txqueuelen 1000  (Local Loopback)

  • Explanation:

    • eth0: Ethernet interface.
    • inet 192.168.1.100: IP address.
    • netmask 255.255.255.0: Subnet mask.
    • ether 00:14:22:01:23:45: MAC address.
    • lo: Loopback interface (localhost).

• Specific Interface

  Pass an interface name to see only its details.

  ifconfig eth0
  • Shows only eth0’s info.

• Enabling an Interface

  Use up to activate an interface.

  sudo ifconfig eth0 up
  • Brings eth0 online (requires root privileges).

• Disabling an Interface

  Use down to deactivate an interface.

  sudo ifconfig eth0 down
  • Shuts off eth0.

• Setting an IP Address

  Assign an IP address and optionally a netmask.

  sudo ifconfig eth0 192.168.1.200 netmask 255.255.255.0
  • Sets eth0 to IP 192.168.1.200 with subnet 255.255.255.0.

• Changing MAC Address (Spoofing)

  Modify the hardware (MAC) address with hw ether.

  sudo ifconfig eth0 hw ether 00:11:22:33:44:55
  • Changes eth0’s MAC address (interface must be down first).

To get help related to the ifconfig command use --help option

$ ifconfig --help
Usage:
  ifconfig [-a] [-v] [-s] <interface> [[<AF>] <address>]
  [add <address>[/<prefixlen>]]
  [del <address>[/<prefixlen>]]
  [[-]broadcast [<address>]]  [[-]pointopoint [<address>]]
  [netmask <address>]  [dstaddr <address>]  [tunnel <address>]
  [outfill <NN>] [keepalive <NN>]
  [hw <HW> <address>]  [mtu <NN>]
  [[-]trailers]  [[-]arp]  [[-]allmulti]
  [multicast]  [[-]promisc]
  [mem_start <NN>]  [io_addr <NN>]  [irq <NN>]  [media <type>]
  [txqueuelen <NN>]
  [[-]dynamic]
  [up|down] ...

  <HW>=Hardware Type.
  List of possible hardware types:
    loop (Local Loopback) slip (Serial Line IP) cslip (VJ Serial Line IP)
    slip6 (6-bit Serial Line IP) cslip6 (VJ 6-bit Serial Line IP) adaptive (Adaptive Serial Line IP)
    ash (Ash) ether (Ethernet) ax25 (AMPR AX.25)
    netrom (AMPR NET/ROM) rose (AMPR ROSE) tunnel (IPIP Tunnel)
    ppp (Point-to-Point Protocol) hdlc ((Cisco)-HDLC) lapb (LAPB)
    arcnet (ARCnet) dlci (Frame Relay DLCI) frad (Frame Relay Access Device)
    sit (IPv6-in-IPv4) fddi (Fiber Distributed Data Interface) hippi (HIPPI)
    irda (IrLAP) ec (Econet) x25 (generic X.25)
    eui64 (Generic EUI-64)
  <AF>=Address family. Default: inet
  List of possible address families:
    unix (UNIX Domain) inet (DARPA Internet) inet6 (IPv6)
    ax25 (AMPR AX.25) netrom (AMPR NET/ROM) rose (AMPR ROSE)
    ipx (Novell IPX) ddp (Appletalk DDP) ec (Econet)
    ash (Ash) x25 (CCITT X.25)

For more details, check the manual with man ifconfig