Configure networking on Azure Linux

Azure Linux uses systemd-networkd as its default network management service. systemd-networkd is a lightweight system service that configures and manages network interfaces declaratively through configuration files.

This article shows you how to manage the systemd-networkd service, where to place network configuration files, how to define common interface configurations such as DHCP and static IP, and how to monitor and troubleshoot network state on an Azure Linux system.

Note

Azure Linux 4.0 is now in preview and is strictly limited to evaluation and testing purposes. It's not suitable for production use.

Prerequisites

  • An Azure Linux system that you can authenticate to with shell access.
  • A user account with sudo privileges, which is required to manage system services and edit network configuration files under /etc/systemd/network/.

Capabilities of systemd-networkd

You can use systemd-networkd on Azure Linux virtual machines (VMs) to perform the following networking tasks:

  • Configure network interfaces with DHCP or static IP addresses.
  • Manage multiple network interface cards (NICs) on a single host.
  • Configure advanced networking features such as VLANs, bridges, and bonded interfaces.
  • Integrate with the DHCP and DNS services that the Azure platform provides.

Manage the systemd-networkd service

Use systemctl to start, stop, restart, and check the status of the systemd-networkd service.

Start the systemd-networkd service

Start the systemd-networkd service using the following command:

sudo systemctl start systemd-networkd

Stop the systemd-networkd service

Note

This action shuts down all networking within the VM, immediately terminating the active SSH session and leaving the VM completely unreachable by any standard means, aside from access through the serial console.

Stop the systemd-networkd service using the following command:

sudo systemctl stop systemd-networkd

Restart the systemd-networkd service

Restart the systemd-networkd service, for example after you change a configuration file, using the following command:

sudo systemctl restart systemd-networkd

Check the service status

Check the systemd-networkd service status and view its most recent log entries using the following command:

sudo systemctl status systemd-networkd

The output shows whether the service is loaded, active, and enabled at boot, along with the most recent log lines that the service produced.

View service logs

View the full log history for the systemd-networkd service using the following command:

journalctl -u systemd-networkd

The output includes every log line that the service has emitted since the system started, which helps you diagnose issues such as failed interface configuration or DHCP problems.

Network configuration files

systemd-networkd reads its configuration from drop-in files in two well-known directories. Each file uses a specific extension that determines what kind of configuration it provides.

The following table describes the directories and file types that systemd-networkd uses:

File or directory Purpose
/etc/systemd/network/ Directory for custom network configurations that you create.
/lib/systemd/network/ Directory for default network configurations that are installed by packages.
.network files Define interface behavior, such as DHCP, static IP, gateway, and DNS.
.netdev files Define virtual devices, such as bonds, bridges, and VLANs.
.link files Define hardware link properties, such as renaming NICs and setting the MTU.

Place your custom configuration files in /etc/systemd/network/. Files in /etc/systemd/network/ take precedence over files with the same name in /lib/systemd/network/.

The following sections provide example network configuration files (.network files) for common scenarios on Azure Linux VMs.

Example: Configure a primary NIC with DHCP

The following example .network file configures the primary network interface (eth0) to obtain its IP address from a DHCP server:

[Match]
Name=eth0

[Network]
DHCP=yes

This is the typical configuration for an Azure Linux VM, where the primary network interface receives its IP address dynamically from the Azure DHCP service.

Save the file with a .network extension under /etc/systemd/network/, for example as /etc/systemd/network/10-eth0.network, and then restart systemd-networkd to apply the change.

Example: configure a secondary NIC with a static IP

The following example .network file configures a secondary network interface (eth1) with a static IP address, gateway, and DNS server. Replace <IP_ADDRESS>, <CIDR>, <GATEWAY_IP>, and <DNS_IP> with values that match your network:

[Match]
Name=eth1

[Network]
Address=<IP_ADDRESS>/<CIDR>
Gateway=<GATEWAY_IP>
DNS=<DNS_IP>

Save the file with a .network extension under /etc/systemd/network/, for example as /etc/systemd/network/20-eth1.network, and then restart systemd-networkd to apply the change.

Monitor and troubleshoot networking

Use the networkctl and ip commands to inspect the current state of your network interfaces and verify that your configuration is correctly applied.

List all known network interfaces

List every network interface that systemd-networkd knows about, along with its type, operational state, and configuration state using the following command:

networkctl list

Show details for a specific network interface

Show detailed status information for a specific interface using the following command. Replace <INTERFACE> with the name of the interface that you want to inspect, such as eth0:

networkctl status <INTERFACE>

The output includes the interface's IP addresses, gateway, DNS servers, and the configuration file that's currently applied to it.

Discover other networkctl commands

See every subcommand and option that networkctl supports using the following command:

networkctl --help

Verify IP addresses and routes

Use the ip commands to verify that the expected IP addresses and routes are configured on the system.

List all assigned IP addresses

List every IP address that's assigned to each network interface, using the following command:

ip addr

List all routes

List every route in the system's routing table using the following command:

ip route

Related content

For more information, see the following upstream resources:

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