Comment 19 for bug 1763608

Just ran into this when installing devstack on Ubuntu 18. I configured netplan with:

  vlans:
    eno1.818:
      id: 818
      link: eno1

When I apply'ed this, it created the link, but did not bring it up.

eno1.818 is referenced in the devstack configuration the "PUBLIC_INTERFACE". It gets plumbed into Open vSwitch to provide neutron a link to the outside world. Neutron expects that this interface already exists and is "up".

The equivalent for Ubuntu 16, which did work:

auto eno1.818
iface eno1.818 inet manual
    vlan-raw-device eno1