systemd-networkd on Ubuntu 16.04 LTS (Xenial)

My OpenStack cloud depends on Ubuntu, and the latest release of OpenStack-Ansible (what I use to deploy OpenStack) requires Ubuntu 16.04 at a minimum. I tried upgrading the servers in place from Ubuntu 14.04 to 16.04, but that didn’t work so well. Those servers wouldn’t boot and the only recourse was a re-install.

Once I finished re-installing them (and wrestling with several installer bugs in Ubuntu 16.04), it was time to set up networking. The traditional network configurations in /etc/network/interfaces are fine, but they weren’t working the same way they were in 14.04. The VLAN configuration syntax appears to be different now.

But wait ― 16.04 has systemd 229! I can use systemd-networkd to configure the network in a way that is a lot more familiar to me. I’ve made posts about systemd-networkd before and the simplicity in the configurations.

I started with some simple configurations:

root@hydrogen:~# cd /etc/systemd/network root@hydrogen:/etc/systemd/network# cat enp3s0.network [Match] Name=enp3s0 [Network] VLAN=vlan10 root@hydrogen:/etc/systemd/network# cat vlan100.netdev [NetDev] Name=vlan10 Kind=vlan [VLAN] Id=10 root@hydrogen:/etc/systemd/network# cat vlan100.network [Match] Name=vlan100 [Network] Bridge=br-mgmt root@hydrogen:/etc/systemd/network# cat br-mgmt.netdev [NetDev] Name=br-mgmt Kind=bridge root@hydrogen:/etc/systemd/network# cat br-mgmt.network [Match] Name=br-mgmt [Network] Address=172.29.236.21/22

Here’s a summary of the configurations:

Physical network interface is enp3s0 VLAN 10 is trunked down from a switch to that interface Bridge br-mgmt should be on VLAN 10 (only send/receive traffic tagged with VLAN 10)

Once that was done, I restarted systemd-networkd to put the change into effect:

# systemctl restart systemd-networkd

Great! Let’s check our work:

root@hydrogen:~# brctl show bridge name bridge idSTP enabled interfaces br-mgmt8000.0a30a9a949d9no root@hydrogen:~# networkctl IDX LINKTYPEOPERATIONAL SETUP 1 loloopbackcarrierunmanaged 2 enp2s0etherroutableconfigured 3 enp3s0etherdegradedconfigured 4 enp4s0etheroffunmanaged 5 enp5s0etheroffunmanaged 6 br-mgmtetherno-carrierconfiguring 7 vlan10etherdegradedunmanaged 7 links listed.

So the bridge has no interfaces and it’s in a no-carrier status. Why? Let’s check the journal:

# journalctl --boot -u systemd-networkd Jan 15 09:16:46 hydrogen systemd[1]: Started Network Service. Jan 15 09:16:46 hydrogen systemd-networkd[1903]: br-mgmt: netdev exists, using existing without changing its parameters Jan 15 09:16:46 hydrogen systemd-networkd[1903]: br-mgmt: Could not append VLANs: Operation not permitted Jan 15 09:16:46 hydrogen systemd-networkd[1903]: br-mgmt: Failed to assign VLANs to bridge port: Operation not permitted Jan 15 09:16:46 hydrogen systemd-networkd[1903]: br-mgmt: Could not set bridge vlan: Operation not permitted Jan 15 09:16:59 hydrogen systemd-networkd[1903]: enp3s0: Configured Jan 15 09:16:59 hydrogen systemd-networkd[1903]: enp2s0: Configured

The Could not append VLANs: Operation not permitted error is puzzling. After some searching on Google, I found a thread from Lennart :

> After an upgrade, systemd-networkd is broken, exactly the way descibed > in this issue #3876[0] Please upgrade to 231, where this should be fixed. Lennart

But Ubuntu 16.04 has systemd 229:

# dpkg -l | grep systemd iilibpam-systemd:amd64229-4ubuntu13amd64system and service manager - PAM module iilibsystemd0:amd64229-4ubuntu13amd64systemd utility library iipython3-systemd231-2build1amd64Python 3 bindings for systemd iisystemd229-4ubuntu13amd64system and service manager iisystemd-sysv229-4ubuntu13amd64system and service manager - SysV links

I haven’t found a solution for this quite yet. Keep an eye on this post and I’ll update it once I know more!