Comment 3 for bug 1637118

Also note in the commit message here:

https://review.openstack.org/#/c/79801/

"Note: a patch to fix the neutron port-security-enabled extension will follow which allows one to boot instances on networks without subnets and ports without fixedips."

That's this code:

https://github.com/openstack/nova/blob/a6053dd608a96ae57521a74b0d6f0f24d7efe75c/nova/network/neutronv2/api.py#L756

So if the network doesn't have port security enabled then we don't need subnets.

However, that happens in nova-compute long after we've validated the request here:

https://github.com/openstack/nova/blob/a6053dd608a96ae57521a74b0d6f0f24d7efe75c/nova/network/neutronv2/api.py#L1597

And failed as noted in this bug.