Ubuntu – Ubuntu 18.04: How to create a persistent dumthe network interface

18.04interfacenetplannetworking

I am trying to create a dummy network interface on a Ubuntu 18.04 server. Here is how I would do it on my previous Ubuntu 16.04 servers:

In /etc/network/interfaces.d/dummy.cfg, write:

auto dummy0
iface dummy0 inet static
address 192.168.98.1
netmask 255.255.255.0

And then add source /etc/network/interfaces.d/dummy.cfg in /etc/network/interfaces/

From what I understand, Ubuntu 18.04 does not use /etc/network/interfaces anymore, we should use netplan instead. Apparently netplan does not support the creation of virtual interface (!) https://bugs.launchpad.net/ubuntu/+source/nplan/+bug/1743200.

I can create the dummy interface with the iproute2 toolkit instead:

$ ip link add dummy0 type dummy
$ ip addr add 192.168.98.1/24 dev dummy0
$ ip link set dummy0 up

But this interface will disappear after reboot, as one would expect.

How can I create such a dummy network interface that will persist after reboot?

Best Answer

I had the same problem on 18.04 server and directly used the systemd-networkd way of configuring interfaces:

I created 2 files in /etc/systemd/network/:

  1. 10-dummy0.netdev

    [NetDev]
Name=dummy0
Kind=dummy

  2. 20-dummy0.network

    [Match]
Name=dummy0

[Network]
Address=192.168....
Address=fe80::.....

On boot the dummy interface is created automatically with IPv4 and IPv6 addresses an is shown in ip addr . Also systemctl restart systemd-networkd should create the interface.

I filed a bug on netplan, please support: https://bugs.launchpad.net/netplan/+bug/1774203

The docs:

https://www.freedesktop.org/software/systemd/man/systemd.netdev.html# https://www.freedesktop.org/software/systemd/man/systemd.link.html# https://www.freedesktop.org/software/systemd/man/systemd.network.html#

Related Question