Master Linux Network Configuration Across Distributions: netplan, nmcli, systemd‑networkd, and ifupdown

1. Ubuntu/Debian: netplan (YAML)

Since Ubuntu 18.04, Canonical delegates network configuration to netplan, which translates YAML files into backend configurations for systemd‑networkd or NetworkManager. Configuration files reside in /etc/netplan/ and typically use names like 01-netcfg.yaml or 50-cloud-init.yaml.

Static IP example:

network:
  version: 2
  renderer: networkd
  ethernets:
    enp0s3:
      dhcp4: no
      addresses: [192.168.1.100/24]
      routes:
        - to: default
          via: 192.168.1.1
      nameservers:
        addresses: [8.8.8.8, 1.1.1.1]

Key pitfalls: YAML is indentation‑sensitive (spaces only), dhcp4: no must be explicit, and the newer routes syntax replaces the deprecated gateway4. Test changes with sudo netplan try (auto‑rollback on failure) before applying with sudo netplan apply. For a quick DHCP setup, use a three‑line YAML with dhcp4: yes.

2. CentOS/RHEL: NetworkManager + nmcli

From CentOS 7 onward, NetworkManager is the primary manager. The nmcli CLI lets you configure networking without editing files directly.

Show current status:

$ nmcli device status
DEVICE  TYPE      STATE      CONNECTION
ens33   ethernet  connected  ens33
lo      loopback  unmanaged  --

Configure a static IP:

$ nmcli con mod ens33 ipv4.addresses 10.0.0.50/24
$ nmcli con mod ens33 ipv4.gateway 10.0.0.1
$ nmcli con mod ens33 ipv4.dns 8.8.8.8
$ nmcli con mod ens33 ipv4.method manual

Reload and activate the connection with nmcli con reload and nmcli con up ens33. Verify the settings using nmcli device show ens33 | grep IP. Configuration files live under /etc/NetworkManager/system-connections/, but direct file edits are rarely needed. CentOS 8/RHEL 8 also provide nmstate, a declarative tool similar to netplan, though nmcli remains the most reliable.

3. Arch Linux: systemd‑networkd

Arch follows the KISS principle; systemd‑networkd is the lightweight network manager within the systemd ecosystem.

Configuration files are placed in /etc/systemd/network/ with a .network suffix. Files are processed in lexical order, allowing numeric prefixes to control priority.

DHCP configuration:

[Match]
Name=enp0s3

[Network]
DHCP=yes

[DHCP]
RouteMetric=100

Static IP configuration:

[Match]
Name=enp0s3

[Network]
Address=192.168.1.100/24
Gateway=192.168.1.1
DNS=8.8.8.8
DNS=1.1.1.1

After editing, restart the service with sudo systemctl restart systemd-networkd and enable systemd-resolved for DNS handling: sudo systemctl enable --now systemd-resolved.

4. Alpine Linux: ifupdown

Alpine uses the classic ifupdown implementation from busybox. The main file is /etc/network/interfaces, mirroring Debian’s older style.

DHCP example:

auto eth0
iface eth0 inet dhcp

Static IP example:

auto eth0
iface eth0 inet static
  address 192.168.1.100
  netmask 255.255.255.0
  gateway 192.168.1.1

DNS servers are defined in /etc/resolv.conf (e.g., nameserver 8.8.8.8, nameserver 1.1.1.1). Apply changes with /etc/init.d/networking restart or by restarting the network service.

5. Common verification commands

After applying configurations, run the following to confirm connectivity:

ip addr – shows assigned IPs.

ip route – displays the routing table and default gateway.

ping – tests reachability of the gateway and external DNS.

ss – checks listening sockets (e.g., ss -tulpn | grep :80).

resolvectl – inspects DNS resolver status on systemd‑based systems.

6. Systematic troubleshooting flow

When connectivity fails, follow these steps (covers ~90% of cases):

Physical layer : ip link show; if the interface is DOWN, bring it up with ip link set eth0 up. Verify VM bridge settings if applicable.

IP configuration : ip addr; ensure an address is present. In DHCP mode, a missing address may indicate a dead DHCP server or MAC filtering.

Routing : ip route; confirm a default via … entry exists.

DNS : If IP ping works but hostnames do not, check /etc/resolv.conf or resolvectl status. Remember that some distros manage resolv.conf automatically.

Firewall : Temporarily disable iptables or firewalld to see if rules are blocking traffic. In production, adjust rules rather than leaving the firewall off.

SELinux (CentOS/RHEL) : Query status with getenforce. If Enforcing interferes, set permissive mode with setenforce 0 for testing, but apply proper policies for long‑term use.

Following this logical flow lets you quickly locate and fix most network issues across any Linux distribution.