Linux Networking Configuration

Temporary: the ip command

sudo ip addr add 192.168.1.50/24 dev eth0    # add an IP
sudo ip addr del 192.168.1.50/24 dev eth0    # remove it
sudo ip link set eth0 up                     # bring interface up
sudo ip route add default via 192.168.1.1   # default gateway
sudo ip route add 10.10.0.0/16 via 192.168.1.254  # static route

Perfect for testing and troubleshooting — but everything here vanishes on reboot. Verify with ip addr and ip route (full list in Linux commands for network engineers).

Persistent on Ubuntu: netplan

Ubuntu reads YAML from /etc/netplan/. A static-IP example:

network:
  version: 2
  ethernets:
    eth0:
      addresses: [192.168.1.50/24]
      routes:
        - to: default
          via: 192.168.1.1
      nameservers:
        addresses: [1.1.1.1, 8.8.8.8]

Apply with sudo netplan apply. YAML is indentation-sensitive — two spaces, never tabs (see YAML explained).

Persistent on RHEL/Fedora: nmcli

sudo nmcli con mod eth0 ipv4.addresses 192.168.1.50/24 \
  ipv4.gateway 192.168.1.1 ipv4.dns "1.1.1.1 8.8.8.8" ipv4.method manual
sudo nmcli con up eth0

NetworkManager owns the config; nmcli con show lists connections.

DNS: where it actually lives now

/etc/resolv.conf is often a symlink managed by systemd-resolved — editing it directly gets overwritten. Set DNS in netplan/nmcli as above, and check what is really in use with resolvectl status. Test resolution with dig.

The verification habit

After any change, run the same ladder you would on any host: ip addr → ip route → ping gateway → ping 8.8.8.8 → dig google.com. It is the layered method in five commands.

Frequently asked questions

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