Networking Fundamentals

Linux has powerful built-in networking capabilities. Whether you are configuring a server, debugging connectivity issues, or securing a firewall, understanding Linux networking tools is essential.

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Network Interfaces

A network interface is the point of connection between your system and a network. Common interface names:

Name Pattern	Type
eth0, ens33	Ethernet (wired)
wlan0, wlp2s0	Wireless
lo	Loopback (localhost, 127.0.0.1)
docker0, br-xxx	Bridge (Docker, containers)
veth	Virtual Ethernet (containers)

ip — Network Configuration

The ip command is the modern replacement for the older ifconfig:

ip addr show                     # show all interfaces and IP addresses
ip addr show eth0                # show specific interface
ip link show                     # show link-layer information
ip route show                    # show routing table
ip neigh show                    # show ARP table (neighbours)

Configuring IP Addresses

# Temporary (lost on reboot)
sudo ip addr add 192.168.1.100/24 dev eth0
sudo ip link set eth0 up

# Permanent — depends on distribution
# Ubuntu/Debian: /etc/netplan/*.yaml
# Fedora/RHEL: /etc/NetworkManager/system-connections/

Example Netplan configuration (Ubuntu):