ifconfig – Simple Guide

What is ifconfig?

ifconfig (interface configuration) is a Linux/Unix command used to view and configure network interfaces on a system.

It shows details like IP address, MAC address, interface status, and packet statistics.

Why is ifconfig used?

• Check IP address of the system
• Verify network interface status (up/down)
• Troubleshoot network connectivity issues
• Check packet transmission and errors
• Temporary network configuration

Basic ifconfig Usage

1. Display all network interfaces

ifconfig

2. Display a specific interface

ifconfig eth0

3. Bring an interface up or down

ifconfig eth0 up
ifconfig eth0 down

4. Assign IP address (temporary)

ifconfig eth0 192.168.1.10 netmask 255.255.255.0

Understanding ifconfig Output

• inet – IPv4 address
• inet6 – IPv6 address
• ether – MAC address
• RX/TX – Received and transmitted packets
• errors/dropped – Network issues indicator

ifconfig Troubleshooting (Common Issues)

1. Command not found

ifconfig: command not found

Cause: net-tools package not installed (common in modern Linux).

Fix:

sudo yum install net-tools
sudo apt install net-tools

2. Interface has no IP address

Cause: DHCP not assigned or interface down.

Fix:

ifconfig eth0 up
systemctl restart network

3. Network not working but interface is up

Possible causes: Wrong gateway, DNS issue, routing problem.

Check:

route -n
cat /etc/resolv.conf

Important Notes

• ifconfig is deprecated in many modern Linux systems
• Recommended replacement: ip addr, ip link
• Still widely asked in interviews and legacy systems

Key Interview Points

• Used to view and configure network interfaces
• Changes made using ifconfig are temporary
• Useful for quick network troubleshooting