This directory contains sample configuration files for setting up a bridge (br0) and a permanent tap interface (tap0) using systemd's networkd network manager. The tap interface can be used, for example, to run a virtual machine that appears as a real machine on the host's Ethernet network. Assumptions: - The host's Ethernet interface is eth0. - The host uses IPv4 DHCP for network configuration. Note: only perform the following steps over a physical login to the host since the configuration involves bringing the host's networking down. 1. Switch to systemd-networkd for network configuration. Overall, the goal of this step is to disable the currently used network manager and enable systemd-networkd. First check if systemd-networkd is already used: # systemctl status systemd-networkd If it's enabled and running, skip to step 2. Otherwise, identify the currently used network manager. The possible options depend on the distribution used so consult the relevant documentation for details. One common option is the GNOME network manager: # systemctl status NetworkManager If it's enabled and running, stop and disable: # systemctl stop NetworkManager # systemctl disable NetworkManager For Debian-based distributions a common approach is to define the network configuration in the /etc/network/interfaces file. To disable this method, perform the following steps: # systemctl stop networking # mv /etc/network/interfaces /etc/network/interfaces.disabled Once the current network manager is disabled, proceed to step 2. 2. Configure bridged networking using systemd-networkd. Copy configuration files found in this directory to /etc/systemd/network/ (see the comment at the beginning of each file for its purpose): # cp *.netdev *.network /etc/systemd/network/ Note: if you are already using systemd-networkd, then you may already have some configuration in /etc/systemd/network/. If the existing configuration conflicts with this setup (for example, you already have a configuration for eth0), then you will need to remove the relevant files. Then adjust the following to match your setup: - Ethernet interface name if not eth0: 20-br0-eth0.network (both name and content) - Bridge MAC address: 10-br0.netdev Use your Ethernet interface's address as your bridge address, which you can obtain with: # ip link show eth0 - Tap user/group: 10-tap0.netdev For example, set to the user/group that will run the VM that will use this tap interface. 3. Test and enable networking using systemd-networkd. Once the configuration is complete, start/restart systemd-networkd and verify networking is configured correctly. # systemctl restart systemd-networkd # systemctl status systemd-networkd # ip addr show br0 # ip addr show tap0 Specifically, verify that: - The br0 MAC address is correct. - The br0 interface is assigned (via DHCP) an IP address and, if a fixed IP is used, it's what's expected. - Try to ping example.org to confirm the overall network (routing, DNS) is functional. If everything looks good, enable systemd-networkd: # systemctl enable systemd-networkd You may also want to reboot the host and performs the above verifications one more time.