Master Linux Network Interface Management: Essential Commands and Real-World Examples

ifconfig command

ifconfig

is a basic utility for displaying and configuring network interfaces.

# Example: view all interfaces
ifconfig -a

# Enable or disable an interface
sudo ifconfig eth0 up
sudo ifconfig eth0 down

# Set IP address and netmask
sudo ifconfig eth0 192.168.1.2 netmask 255.255.255.0

ip command

The ip suite replaces ifconfig with more powerful and flexible syntax.

# Example: list all interfaces
ip link show

# Enable or disable an interface
sudo ip link set eth0 up
sudo ip link set eth0 down

# Configure IP address and netmask (CIDR notation)
sudo ip address add 192.168.1.2/24 dev eth0

route command

route

manages static routing tables.

# Show current routing table
route -n

# Add a static route
sudo route add -net 192.168.2.0 netmask 255.255.255.0 gw 192.168.1.1

netstat command

netstat

displays network connections, routing tables, and interface statistics.

# List all network connections
netstat -a

# Show listening ports only
netstat -l

traceroute command

traceroute

traces the path packets take to a destination.

# Trace route to a host
traceroute www.example.com

ping command

ping

tests reachability of a remote host.

# Ping a host
ping www.example.com

ss command

ss

shows socket statistics, replacing many netstat uses.

# Display all sockets
ss -a

# Show only TCP connections
ss -t

nmcli (NetworkManager CLI)

nmcli

configures network connections via NetworkManager.

# List all connections
nmcli connection show

# Modify IPv4 address of eth0
sudo nmcli connection modify eth0 ipv4.addresses "192.168.1.2/24"

iw command (wireless management)

iw

handles wireless interfaces.

# Show wireless devices
iw dev

# Scan for available networks
sudo iw dev wlan0 scan

# Connect to a Wi‑Fi network
sudo iw dev wlan0 connect "YourSSID" key 0:YourPassphrase

ethtool command

ethtool

inspects and configures Ethernet adapter parameters.

# Show detailed interface info
ethtool eth0

# Set speed and duplex mode
sudo ethtool -s eth0 speed 100 duplex full

Configuring DNS

Two common methods are editing /etc/resolv.conf directly or using systemd-resolved.

# Edit resolv.conf manually
sudo nano /etc/resolv.conf

# Enable systemd-resolved and link stub resolver
sudo systemctl start systemd-resolved
sudo systemctl enable systemd-resolved
sudo ln -sf /run/systemd/resolve/stub-resolv.conf /etc/resolv.conf

Policy routing with iproute2

The ip route command can create advanced routing rules.

# Add a policy route
sudo ip route add 192.168.3.0/24 via 192.168.1.1 dev eth0

Connecting VPN via NetworkManager

# Import an OpenVPN configuration file
sudo nmcli connection import type openvpn file example.ovpn

# Activate the VPN connection
sudo nmcli connection up my-vpn

firewall-cmd (firewalld management)

# Start and enable firewalld service
sudo systemctl start firewalld
sudo systemctl enable firewalld

# Open TCP port 80 permanently and reload
sudo firewall-cmd --add-port=80/tcp --permanent
sudo firewall-cmd --reload

iptables for advanced network settings

# Port forwarding (DNAT) from host port 80 to internal server
sudo iptables -t nat -A PREROUTING -p tcp --dport 80 -j DNAT --to-destination 192.168.1.2:80

# Enable masquerading for outbound traffic
sudo iptables -t nat -A POSTROUTING -j MASQUERADE

By mastering these commands, Linux administrators gain a comprehensive toolbox for configuring interfaces, managing IP addressing, routing, DNS, wireless networks, VPNs, firewalls, and packet filtering, ultimately ensuring stable, secure, and efficient network operation.