$ Linux Command

Network

ifconfig

Show or configure network interfaces on older systems.

networkinterfaceaddresslegacy

Additional Notes

ifconfig displays and changes network interface settings. It comes from the older net-tools package and is still seen in tutorials, recovery environments, embedded systems, and older distributions.

Modern Linux systems usually prefer the ip command: ip addr, ip link, and ip route. Learn ifconfig for compatibility, but use ip for current administration.

Syntax

ifconfig [interface]
ifconfig interface [address] [options]

Parameters

  • interface: Network interface such as eth0, ens33, wlan0, or lo.
  • address: IPv4 address to assign to the interface.
  • options: Interface state, netmask, broadcast, MTU, and hardware-address settings.

Common Options

  • No arguments: Show active interfaces.
  • -a: Show all interfaces, including inactive ones.
  • INTERFACE: Show one interface.
  • up: Bring an interface up.
  • down: Bring an interface down.
  • netmask MASK: Set an IPv4 netmask.
  • broadcast ADDRESS: Set broadcast address.
  • mtu SIZE: Set interface MTU.

Examples

ifconfig

Show active network interfaces.

ifconfig -a

Show active and inactive interfaces.

ifconfig eth0

Inspect one interface.

sudo ifconfig eth0 192.168.1.50 netmask 255.255.255.0 up

Assign an address and bring the interface up.

sudo ifconfig eth0 down

Disable an interface temporarily.

Practical Notes

  • Changes made with ifconfig are usually temporary and disappear after reboot or network-manager restart.
  • On modern systems, equivalent commands are often ip addr show, ip link set dev eth0 up, and ip addr add ADDRESS dev eth0.
  • Be careful changing an interface over SSH; you can disconnect yourself.