systemd-networkd

There are a number of benefits to using systemd-networkd, as an alternative to Debian’s networking scripts. Providing networking for virtual machines using systemd-networkd is comparable to providing networking for virtual machines using Ubuntu’s netplan.

Configuration

Enable systemd-networkd;

systemctl enable systemd-networkd

Move the interfaces file to stop Debian reading from it;

mv /etc/network/interfaces /etc/network/interfaces.moved_to_systemd-networkd

Do the same for the /etc/network/interfaces.d directory if required.

Creating Bridges

Create a file for each bridge in /etc/systemd/network as a .netdev file. For instance, /etc/systemd/network/br4.netdev;

[NetDev]
Name=br4
Kind=bridge

The name does not need to be in a specific format. br4 was chosen here because the configuration was migrated from an old /etc/network/interfaces configuration.

Physical network devices do not need to be created in systemd-networkd. The names of physical devices can be discovered with the ip link command.

Creating Networks

Internet Protocol can be added to a network device as in the following example file, /etc/systemd/network/br4-ip.network;

[Match]
Name=br4

[Network]
Address=172.27.4.13/24
Gateway=172.27.4.1
DNS=172.27.4.1

Creating VLANs

VLANs are defined as network devices, each in their own .netdev file. The following example is /etc/systemd/network/vlan4.netdev;

[NetDev]
Name=vlan4
Kind=vlan

[VLAN]
Id=4

Binding VLANs to Bridges

The following file, /etc/systemd/network/vlan4.network, binds VLAN 4 (defined above as a network device) to the bridge;

[Match]
Name=vlan4

[Network]
Bridge=br4

Binding Bridges and VLANs to Devices

The following file, /etc/systemd/network/eno1.network, binds both a bridge (untagged, also called a native VLAN), to a physical port.

[Match]
Name=eno1

[Network]
Bridge=br3
VLAN=vlan4