Comment 8 for bug 2069543

Thanks Tobias for the config info!

This way I could reproduce this bug on current master:

devstack e2aeab1b
neutron cdb644574a

$ egrep ISOLATE_VIF local.conf
OS_VIF_OVS_ISOLATE_VIF=True

$ ack isolate_vif /etc/{nova,neutron}
/etc/nova/nova.conf
140:isolate_vif = True

/etc/nova/nova-cpu.conf
139:isolate_vif = True

/etc/neutron/neutron.conf
2635:isolate_vif = True

Out of which I believe only nova-cpu.conf matters. Setting the same in nova.conf and neutron.conf is ignored, but does not hurt either.

openstack network create net0
openstack subnet create --network net0 --subnet-range 10.0.100.0/24 subnet0
openstack port create --network net0 --fixed-ip ip-address=10.0.100.10 port0
openstack network trunk create --parent-port port0 trunk0
openstack server create --flavor cirros256 --image cirros-0.6.2-x86_64-disk --nic port-id=port0 vm0 --wait

$ sudo ovs-vsctl find Port name=tap$( openstack port list --server vm0 -f value -c ID | cut -b 1-11 ) | egrep '(tag|trunks|vlan_mode)'
tag : 4095
trunks : []
vlan_mode : []

My first guess for a root cause is that in neutron we had these changes:

$ git log --oneline --no-merges --grep='dead vlan' -2
0ddca28454 Make sure "dead vlan" ports cannot transmit packets
7aae31c9f9 Make the dead vlan actually dead

However we missed changing os_vif's isolate_vif related behavior accordingly.

I hope to propose a fix soon.