ifconfig – Legacy Network Interface Configuration

ifconfig (interface configuration) is a classic Unix/Linux command for configuring, managing, and displaying network interface parameters. While largely superseded by the ip command from iproute2, ifconfig remains widely used and recognized. It allows administrators to view IP addresses, configure interfaces, enable or disable network adapters, and set various network parameters.

Key Features

• Interface Display – View IP addresses, MAC addresses, and statistics
• IP Configuration – Assign static IP addresses to interfaces
• Interface Control – Bring interfaces up or down
• MTU Settings – Configure Maximum Transmission Unit
• Promiscuous Mode – Enable packet sniffing capabilities
• Hardware Address – View and change MAC addresses

Installation

# Debian/Ubuntu
sudo apt install net-tools

# RHEL/CentOS/Fedora
sudo dnf install net-tools

# Arch Linux
sudo pacman -S net-tools

Common Usage Examples

# Display all interfaces
ifconfig -a

# Show specific interface
ifconfig eth0

# Assign IP address
sudo ifconfig eth0 192.168.1.100 netmask 255.255.255.0

# Bring interface up/down
sudo ifconfig eth0 up
sudo ifconfig eth0 down

# Change MTU
sudo ifconfig eth0 mtu 9000

# Enable promiscuous mode
sudo ifconfig eth0 promisc

# Change MAC address
sudo ifconfig eth0 hw ether 00:11:22:33:44:55

Use Cases

ifconfig is useful for quick network diagnostics, legacy system administration, learning networking basics, simple IP configuration, and compatibility with older scripts and documentation.

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